It's whatever you want to pay for it. There are sellers that break these things up on EBay and sell them for £200 plus - if you are happy with that then fine. I've picked up Fender necks for £100 before but you have to really search EBay and strike early. What's the figure you've been quoted? In terms of fakes, pretty much what Steve said really. If it's a nice neck, it'll feel good. If you have any doubts and are not sure, just walk away.