Is yours a model where, on the uppers, you need to replace the whole control arm? If so, $500 seems a little low for a shop to replace the upper control arms and the lower ball joints. I was quoted $1000 at most places in St Louis.
If you are replacing just 4 balljoints and no control arms, then $500 is prob about right.
I had one lower ball joint replaced by a shop and it cost $275 with alignment. I'm guessing, while it was apart, if they needed to replace the upper balljoint (without replacing the control arm) it would not have been too much more (just the cost of the part). I basically shopped around and went with the shop that had the least upcharge on the part (some were kinda ridiculous)
This summer I plan on replacing the upper control arms myself, then taking it to the same shop, have them do the other lower and align it. I am not comfortable taking apart what needs to be removed to do the lowers. The uppers seem to be 3 bolts off, 3 bolts on.