Let me start off by saying my affiliate marketing and CPA strategy is more based on content marketing than paid traffic and paid advertising. That said I do run eCommerce businesses and do utilize Facebook Ads, Adsense, Pinterest Ads, etc.

Generally speaking affiliate programs don't pay enough to warrant running paid traffic. When it comes to something like Google Adsense most people will tell you don't run ads unless you're making at least $15 per sale. There's a reason for that because ad programs, especially Adsense, are often cost prohibitive for cheaper or lower cost products.

With Affiliate Marketing you have little to no control over the sales process so you're reliant on your affiliate having that streamlined. You also oftentimes can't use tracking pixels to truly know how well your ads are performing as you don't have control over the checkout process.

While it's possible to make money running ads, more often than not it's not worthwhile. If you have a CPA offer in a niche without a lot of ad competition and you can laser focus you're targeting it can work but personally for all the reasons mentioned above I choose not to partake.