That's a good price. I paid not quite that for my 4,1 last September. Did the same flash to 5,1 and upgraded the CPU to a w3680. Added a PCIe SSD too. Haven't upgraded the RAM or GPU yet but looking forward to doing so!
May I ask where you bought yours from?
----------
For anyone interested, it looks like the OP may have bought that 5,1. Check out this thread:
https://forums.macrumors.com/threads/1744637/