We must have done our wire sizing incorrectly if you're showing the wire would cost us $15,000 to go 500 feet. That would definitely be a huge reason to go to the DC run with multiple inverters, batteries, and charge controllers OR to go with the transformer.
When I double the 500 feet in the calculator to 1000 feet (which I still don't understand if I need to do this or why, since it's a 500 foot run) then it comes up with 4/0 cable which is
around the $30 a foot you mentioned. So I assume not doubling that 500 foot run was my error.