Where I work the blades we get I believe run about $60.00 per diamond blade, but we buy them in mass quantities and probably go through a dozen or more per year.
As you can imagine, we cut...A LOT.
Once in a great while on a big commercial job we'll have two demo saws and a table saw running all day long.
As far as the quality of the blades we use, I think they are pretty decent. No complaints from me over a $60.00 blade.