Is $5K a right price for a investigational 2.5 ton and condensor coil? Installed.?

Why is the black square on my digital...
Answers:    That's way too high for a unusual coil, unless it's solid gold. Entire condensers aren't that much even with the latest compressor.
Now if you are talking about a unmarked condensing unit, indoor coil and new copper chain set installed with a 10 year parts and labor warranty unless it's 16 SEER or higher you are still too elevated depending on the brand.
If it's a Trane or Rheem 16 SEER with all spanking new indoor coil, variable speed air handler, (you can't grasp high SEER without a changeable speed blower) line set, new thermostat and 10 year parts and labor warranty you own a very good price.
Putting a tentative condenser on an old coil and line set is call HACKING, and you won't get the efficiency you are paying for. You could remarkably well get more problems than you want.
Loud HVAC part?
I rewarded a little more than that for a new high-ranking efficiency furnace and AC unit (3 ton) plus a topical thermostat that can be programmed. Also included two new return air ducts.
There be a hole contained by my pool....
That sounds approaching a fair price.