My MIL is gluten free and boy does my grocery bill go up when she stays with us for a few weeks.
Like others have said, I find it is cheaper and better to not try and use substitute products but find recipes that just don't have gluten. I have a really good flourless chocolate cookie recipe and another for peanut butter cookies. I also make flourless chocolate cake and flan for desserts for her. For pasta, I use asian rice noodles and do pad thai (you need gluten free soy sauce.) For sauces, I usually make all from scratch using cornstarch. She is always with us for Thanksgiving and I have come up with a really delicious gravy using pureed caramelized onions.
Whole foods is a great but expensive source for times you just have to have bread or pizza or rolls. And I agree that the prices and choices have come way down from where they were. It has been great for her that this has become so mainstream. Makes it much easier to eat out.