If they don't know the work/effort that goes into the project they won't appreciate it, and why give it to them if they're not going to appreciate it? I'd be selfish too! In some ways I am. However, if I make something for someone and all the while I'm making it I'm thinking of them, then in the end, I feel compelled to give it to them with a note informing I had a wonderful time reminiscing of them.
If you want to find out if family members will appreciate something you make for them, make them a hotpad, pillowcase, or something small and see how they take care of it.
Next time your SIL brags about her bownies, remind her you can pronounce the ingredients in yours.