I've been out of town. I just got your PM and replied.
I paid about $4500 total. But, I have a concrete tile roof (added cost) and my tank sits directly under a roof joist that I was not willing to cut/modify for the tubes. So, that required extra elbows and a few extra feet of tubing (more cost).
Plus, I had two solar powered attic fans installed.
FYI, the savings has averaged about $125/month since they have been installed.