Mattresses are one area where I will spend serious money. We usually go for Sealy Posturepedic, but we did try a Tempur-Pedic once too. Didn't love it, but we got a pretty bare-bones model. I think CostCo sells mattress too, though we haven't bought one there.
We generally spend around $1200 to $1700 on a queen mattress, but if you already have a set of box springs and nothing seems wrong with them, don't be pressured into buying a new set. Just buy the mattress. At this point, we buy from our local Macy's furniture store, because they have a good selection of models, and because I've come to hate Sleep Train, where we used to buy our beds.
Oh, and check return policies. A lot of mattress stores will let you swap out a mattress that isn't working for another model, but only once. I always insist on a full return option, even with a 15% restocking fee, just in case I need to go through 2-3 iterations to find the right fit. I usually get it right on the first try these days, but I refuse to be locked into an option that isn't working.
Hey, face-punch if you like, but money is for spending on important things. And good sleep is no joke, especially as you get older and creakier.