I bought two nitto nt555s from a local tire place for $100 per tire + mounting, balancing and old tire disposal...it came out to like $240
This past spring I was on tire rack and they had a closeout deal for kumho ecsta 711...$54 per tire...I picked them up and had them slapped on my rims with all the fees it came out to like $148...and they are much, much better in the rain or dry than my nittos...amazing tread wear too for how much grip they offer.
If you buy from tirerack or other well known and respected online retailor, it's not bad....but if you buy from the cheapest places you should be really to get screwed a few times since some of them aren't honest shops.
If you do buy from a local shop, check the prices before you drop the rims off and look online for a few different tires you want and the sizes you need...that way you don't have to believe what the tire guy says about what tires are good and bad.