I paid £170 for a brand new one with free upgrade to V8 about two years ago. Although now steam-driven by modern standards I still use it on the bike on the yearly Europe trip. Whilst it's not as user-friendly as some of the later models it still does it's job of getting you from start to finish, which, let's be right is all you basically want from a gps.
I think a full package would probably be worth about £50 to me tops as there's so many out there. If it's in good order though it'll still serve well, remember it was the dogs in it's day so must be some use to someone.