First of all, two things...
First.. Lose the all caps posting.. It just comes off as screaming and the people in the community are less likely to read your posts..
Second.. Please don't cross post.. It's against the forum rules. I deleted your post in the Affiliates Looking for shops forum and kept this one mainly because you are not an affiliate looking for shops so the post was inappropriate there...
Now that that is out of the way, the reason an affiliate got a portion of your sale is because they drove a shopper to your shop. It is likely that if the affiliate hadn't sent you the shopper, you wouldn't have got the sale in the first place. So the affiliate isn't "robbing" you of 20% of the profit, they actually gave you 80% of a sale you may have never seen.
If you would rather affiliates not help you market your shop and you don't want to participate in the marketplace, you must opt out of it. All shops are in the marketplace making them available to affiliates by default. If you don't opt out, then affiliates can help sell your stuff.
Edit: just deleted from announce and share affiliate-ready shops as well.. Quit cross-posting...