Low priced goods & Affiliates

I'm considering starting an affiliate program for my ecommerce site, but I'm wondering if it can actually pay off since most of my products are not very expensive. I'm thinking that for a site dealing with small sales such as mine, a flat fee (such as $2/sale) would be better than a percent cut. I'm just wondering if it's woth the trouble. Are power affiliates interested in programs that don't pay big bucks per sale? (obviously adsense works, but per click and per sale are two different things)

Also my site is a niche health care site.

Any advice would be welcome.