What is CPA and Why It Works

CPA (Cost Per Action) is a model where you only pay for specific user actions – such as a registration, subscription, or purchase. This makes budgeting more predictable, increases efficiency, and cuts unnecessary spending. 

Key Strengths of the CPA Model 

Transparency – You only pay for achieved goals. Control – You set your own price per action. 

Profitability – When set up correctly, CPA often delivers the best cost per result. 

Scalability – If your setup works, you can scale fast without added risk. 

Quality Monitoring – You can immediately see which formats and sources convert – and which don’t.

Technical Setup: What You Absolutely Need 

Postback is a must 

It allows the system to register conversions and apply charges accurately. Without postback, CPA simply won’t work – your stats won’t align and billing will be inaccurate. 

Start with a CPM test phase

The test phase is when the system gathers data and calculates your actual cost per lead. You set a test budget – for example, $200 – and launch your campaign on a CPM model. Once the budget is spent, you get a real eCPA value. 

Switching to CPA

Once you know the actual cost per lead for your GEO and format, you set that price in the CPA model. From that moment, the system will buy traffic only at your desired cost per action.

Case Study: Nutra Offer in India (Q1 2025)

GEO: India

Formats: Video, Native Ads (Images)

Traffic Source: xHamster

Goal: Keep eCPA between $1-2

Budget: $100,000+ 

What Was Done 

• The campaign was launched on CPM with 7 ad streams: 4 video creatives and 3 native image creatives

• Different time slots and devices were tested. Postback was set up in advance – confirmed leads were tracked from day one

• All formats ran in parallel without manual filtering – the focus was on identifying the best-performing combinations

During the test phase, no targeting layers (such as time slots, devices, OS, traffic sources, or creatives) were excluded. The campaign was launched “as is,” without bias, to get an objective performance overview and make data-driven decisions later.

Results

Confirmed leads: 85,400 

Average cost per lead: ~$1.05

Before switching to CPA: eCPA ranged from $3–5+

Optimization

• Bids were adjusted based on early eCPA and eCPC performance

• Most traffic was redirected to mobile devices and evening time slots – they delivered better conversion rates

• Some campaigns were scaled manually, others using the platform’s auto-optimization tools

• Optimization was based strictly on confirmed leads – not on clicks or intermediate goals

 Launch & Outcome

• The first stage was a CPM test to identify the best-performing creatives and audiences

• Once eCPA and CR stats were collected, the campaign switched to a CPA model with a fixed bid

• Scaling focused on the strongest combinations (Video 1, Video 2, Native 2), while the others ran in support

• The target cost per lead was achieved and maintained, even as volumes increased
  

• Video formats delivered the highest volume of leads with eCPA between $1.00–$1.06

• Native formats consistently generated leads at a low cost per click

• Evening mobile traffic performed best

• Avoiding early narrowing and strict filters helped identify strong combinations faster

• Postback optimization from day one was a critical success factor

• The model proved scalable and can be applied to other offers