I always tell them, "Sure, but the fabric alone will cost around $250, and the labor will be at least $1000........" That shuts 'em up!
Regarding what people do with the quilts you give them -- I decided, early on, that I'd only give quilts to people I knew would appreciate the time and effort it took to make it, and would take care of it in a reasonable manner. Exceptions to this are charity quilts (Project Linus, etc.), but these are simple quilts & usually tied.
I make my "gift" quilts with the expectation that they will be used (i.e., not put away as an heirloom), but tell the recipient that if they decide they don't want it, to return it to me rather than use it as something to change the car's oil on!