Does anyone know what the current retail rate is for a 1000' spool of 500 MCM XHHW-2aluminum alloy conductor?

It will vary by location of purchase.

I will need to run a total of 1740' (580' X 3) in Western New York southern tier area. Almost fell out of my chair when I saw the numbers for 300 MCM copper.

Copper will give you a heart attack real quick.