I'm not knocking a bargain. Five bucks is great. But you do get what you pay for. I'm using the phpBay plugin for WordPress. From a purely SEO point of view, it's far superior, unless there are options I'm not seeing show up in the source code for the site offered by the $5 script. With phpBay, you can mask both the links and the images so that your source code is not saturated with an eBay affiliate footprint. For this, I'm perfectly willing to pony up $39 for an unlimited license to use the script on as many sites in as many niches as I can crank out. Not only that, WordPress is a better platform for SEO, IMO.
I'm using both BANS and phpBay pro for different sites for different reasons. I'm thrilled with both. I've had to modify both to suit my needs but they're pretty easy to change from a code perspective.