£4500 nowadays doesn't seem extortionate, it really all depends on condition, usability etc. If it is a good running driving truck and pretty much complete with any mods being reversible and you have done the checks you would do with any old vehicle the rest is up to you.
You say you have been out of the scene for a while ? Things have changed, prices have pretty much risen across the board and as the years go by there are less barn finds out there. People tend to know what things are worth because of the internet and auction sites. It is obviously hard to value a vehicle without seeing it in the flesh so the choice is yours, but have you seen any cheaper ? Were they in as good condition ? If so why didn't you buy them ? The choice is limited but if you're not happy with the price then you can always wait until you find one that ticks all the boxes. You could also try looking at recent auction results that will give you an idea of prices. Good luck.