For my smaller house (about 1600 sq ft) my recent AC install (along with a new high efficiency gas furnace) was around $5000, but that price was an HVAC friend of a friend picking up the equipment and doing the install. I got quotes from several hvac companies for about $9000 or so.

That said, it was worth every penny I paid for it, even if I had to pay the "regular" price.

Before the AC install, we were running a portable room AC in the living room, and a window unit AC in my office, and those ran pretty much non stop. They were noisy and only kept the house bearable not comfortable.

Our electric bill is now lower with the central air, but we did also get new windows and attic ventilation around the same time.