PI firms typically run two types of external lead sources: direct lead vendors who sell you leads they generate themselves, and lead generation agencies who manage your paid advertising and capture leads on your behalf. Both fill your intake pipeline. Both send invoices. Comparing their performance fairly — in a way that accounts for how their economics actually work — requires different math than most firms apply.
This is not an argument that one model is better. Both have legitimate advantages and real tradeoffs. The goal is to give you a framework for evaluating them on the same terms so you can make budget decisions based on outcomes rather than pricing structure.
Related guide: See our complete guide to evaluating PI lead vendors — the 7 metrics that define vendor quality and how to build a vendor scorecard.
How Direct Lead Vendors Work
Direct lead vendors generate leads through their own marketing infrastructure — typically mass media, digital advertising, pay-per-call networks, or aggregator relationships — and then sell those leads to law firms. You pay per lead, per call, or in some cases per signed case.
The key characteristics of direct vendor relationships:
- You are buying an output, not a process. You pay for leads delivered. The vendor owns the marketing infrastructure that produces those leads, and you have no visibility into it.
- Pricing is per lead or per case. Your cost per lead is known upfront. Your cost per case depends on conversion — which is partly in your control (intake) and partly a function of lead quality.
- Leads may be shared. Many lead vendors sell the same lead to multiple firms simultaneously. The degree of exclusivity varies by vendor and price tier.
- Vendor performance data is self-reported.When you ask a direct vendor how your leads are performing, they report from their own systems — which don't include what happens to the lead after it enters your firm.
How Lead Generation Agencies Work
Lead generation agencies manage paid advertising campaigns on your behalf — typically Google Ads, Facebook Ads, YouTube, or programmatic display. They spend your ad budget, create and manage the campaigns, and generate leads that come directly to your firm through landing pages or phone numbers.
The key characteristics of agency relationships:
- You are buying a process, not an output. You pay an agency fee (flat or percentage of spend) plus the ad spend itself. The leads are an output of the process, not a direct product.
- Leads are exclusive by default. Campaigns managed for your firm produce leads that go only to your firm. Exclusivity is built into the model.
- You own the audience data.Ad account history, audience signals, and campaign learnings typically belong to you or are accessible to you — depending on the contract. This is a real long-term asset that direct vendor relationships don't produce.
- Costs are split between management fees and ad spend. A typical agency fee runs 10% to 20% of media spend. If you spend $50,000 per month in ads, you might pay $5,000 to $10,000 in management fees on top.
The Comparison Problem: Different Cost Structures
Comparing a direct lead vendor to an agency is genuinely difficult because their cost structures are fundamentally different. Here is where most PI firms make errors in their comparisons.
The Total Cost of Agency Leads
When calculating cost per lead from an agency, you need to include both the ad spend and the management fee. If your agency spends $50,000 on ads, charges $7,500 in fees, and produces 200 leads, your true cost per lead is $287.50 — not $250 (the pure ad spend) and not just the management fee. Both components belong in the numerator.
Many firms inadvertently compare agency CPL based only on ad spend, which makes agencies look more efficient than they are relative to direct vendors.
The True Cost of Direct Vendor Leads
Direct vendor leads look simple to price — you pay a rate per lead. But lead quality affects cost per case, and cost per case is what you actually care about. A direct vendor charging $200 per lead with a 5% conversion rate has a cost per case of $4,000. An agency with a $300 per lead all-in cost and a 10% conversion rate has a cost per case of $3,000. On CPL the vendor wins. On cost per case the agency wins.
This reversal happens constantly and it happens because lead quality differences are invisible until you measure conversion rates.
A Framework for Fair Comparison
To compare direct vendors and agencies on fair terms, evaluate both on the same four dimensions:
1. Total Cost Per Lead (All-In)
For direct vendors: vendor invoice divided by leads received. For agencies: (ad spend + management fees) divided by leads received. Make sure you're including every dollar that went toward that lead.
2. Conversion Rate to Signed Cases
What percentage of leads from this source become signed cases? This requires your intake data, not the vendor's data. The conversion rate reflects both lead quality (vendor's contribution) and your intake process (your contribution) — so be careful about over-attributing conversion differences to lead quality alone. If one source consistently underperforms in conversion, consider whether it might be an intake routing or handling issue before cutting the source.
3. Cost Per Signed Case
Total spend on the source divided by signed cases produced. This is the most decision-relevant metric for comparing sources, and it should be calculated the same way regardless of whether the source is a direct vendor or an agency.
4. Case Quality (If Available)
As you build settlement data by source, layer in average settlement value to see whether cost per case differences reflect case value differences. An agency that produces higher-cost-per-case but higher-value cases may have better economics than a direct vendor with a lower cost per case but lower average settlement.
| Factor | Direct Vendors | Agencies | |
|---|---|---|---|
| What You Buy | Output (leads) | Process (campaign management) | |
| Lead Exclusivity | Often shared | Exclusive by default | |
| Pricing Model | Per lead / per case | Ad spend + management fee | |
| Transparency | Limited | Full campaign visibility | |
| Long-term Asset | None | Audience data & account history | |
| Management Required | Minimal | Ongoing oversight |
The Arguments for Direct Vendors
Direct vendors have real advantages in specific situations:
- Predictable volume. A vendor contracted to deliver a certain lead volume provides more predictable pipeline than digital advertising, which fluctuates with auction dynamics, seasonality, and algorithm changes.
- Simple pricing. Per-lead pricing is easy to understand and easy to budget. There are no management fees, no media buying negotiations, no monthly adjustments.
- No internal management required. Direct vendors handle their own advertising. You receive leads without managing campaigns or vendor strategy.
- Performance-based options. Some direct vendors offer pay-per-case pricing, which shifts the performance risk to the vendor. If they only produce cases you sign, you only pay for results.
The Arguments for Agencies
- Exclusive leads by default.You're not competing with other firms for the same prospect — the lead was generated specifically for your firm.
- Brand and audience building.Agency-managed digital campaigns build your firm's presence in search results and on social platforms. Over time, this creates audience data and brand awareness that direct vendor relationships don't generate.
- Transparency into the process. You can see which campaigns, keywords, and ad types produce the leads — data that helps you optimize over time. Direct vendors give you leads but not the methodology behind them.
- Long-term asset ownership.A well-built Google Ads account history is a real asset. Campaign learnings, audience signals, and quality scores compound over time in a way that vendor relationships don't.
How to Compare Them in Practice
The practical challenge is that you are almost always running both simultaneously, and you need a consistent measurement approach that makes both sources comparable in your reporting.
The most useful approach: normalize all sources to cost per signed case and calculate it consistently. Whether a source is a direct vendor or an agency, the formula is the same — total money spent divided by signed cases produced. Run that calculation monthly for every source, track it quarterly to smooth out volume fluctuations, and review annually to identify long-term trends.
When you do this consistently, direct vendors and agencies become comparable in a way they aren't when you evaluate them on their native metrics (CPL for vendors, campaign ROAS for agencies). The shared metric is cost per case — and that is the metric that reflects your actual marketing efficiency regardless of how the source is structured.
Firms that make this comparison regularly find that their vendor portfolio almost always has unexpected performers in both directions. Some direct vendors that looked expensive on CPL turn out to have excellent cost per case numbers. Some agencies that presented impressive campaign metrics turn out to have weaker conversion rates than expected. The data is often surprising — and surprising data is exactly what makes the measurement worthwhile.
Related guide: See our complete guide to evaluating a PI marketing agency — 7 evaluation criteria, red flags to watch for, and how to hold agencies accountable with data.