In ebay capsules, you earn from clicks, NOT sales. The sales data exist just to show you what people ultimately bought, so you can showcase your products better.
The amount you earn per click varies. In my case, it has been between 3 and 7 cents per click. That's not much individually, but it adds up if you have an eBay capsule on a popular hub. Say 1000 people view one of your hubs this month, and you have a click-through rate of 3% on a good eBay capsule. That could be up to two dollars with no real effort on your part.
I haven't found much success with Amazon yet, but I know other people make serious money through it. I don't think eBay will get you huge returns, but it's a nice supplement, and you may be able to offer things from eBay that you can't find on Amazon (gently used bike equipment or parts, maybe?).