You must sign up to Prime to get to the checkout, but can immediateley cancel it.
There's a US$99 charge for 1 year, this WILL be charged immediatley. You can contact Amazon and request a cancellation and refund which will be granted.
This is within $3 of it's lowest ever price for the US set. It's a 2006 DVD set so i wouldn't be expecting amazing quality, but it's a great show.
Bought it from the UK Amazon for 38 pounds delivered to Aus, (AU$77 current XE) in March. The price seems to go up and down, but presently that would be too high?!