The only part you might want to check first are the forks. If you intend to keep it for a few years see if someone will still service them. Other than that the rest of the parts are just normal parts.
I used to ride one and it was fine. If its in good nick then that sort of money seems fine. But if the forks need a service then you may want to negotiate that into the price.
Apart from the fork issue, any bike is basically just a frame with bits bolted on. The bits are cheap and wear out over time anyway. Make sure the frame is not cracked.
But Whyte are a really good company, the do a lifetime warranty on the bearings. They are not special bearings mind you.