It may depend on the specific Kaffe fabric. I've made several quilts from Kaffe fabrics and never found any that I thought were thin.
As for not buying something and selling later at a higher price, hmmm... does that mean you would be willing to sell your house today for what you paid for it 20 years ago? Whether or not the profit is donated, I think it's a legitimate thing to buy kits (or anything else), hold onto them, and sell later at a higher price. I wish I had thought of it! I do have a friend who is selling parts of her huge stash on ebay. The old Alexander Henry prints, for example, go for much more than their original price.
Edited to add - I am quite sure the fabrics, even if they feel thin, will hold up after they're quilted.