Well, if the service becomes popular, the OP will find himself sitting on a nice rolling account of cash (the funds that haven't yet been spent or returned to donors), which might be capable of generating interest. I can't imagine that income being appreciable (or entirely legally kosher), but who knows?

It's easy to make money on anything that is popular. The "profit" made on top of adding a small fee. on top of Balanced's fee, is so minuscule and quickly eaten by shipping costs.

Right now, I'm more interested in building something that makes a profit just for the hell of it. All my other side-projects are making me absolutely nothing. ...nothing but resume padding :)

Affiliates referral. There's a small revenue also on top of the charges and fees that Balanced cost but that part is primarily to cover the cost of shipping.

Well any product links could be his affiliate link to amazon - it won't be millions but if the site gets popular it can add up.

The intention with the site is not be get rich but it would be fun to have a profit at all.

Having said that, any product link is very very different from a product link that a close friend has picked out. Chances are you desire the same. For example, I trust Kristin's research into binoculars https://wishlistgranted.com/9eca0593/