Hey Dean!
The short answer is they're worth whatever someone is willing to pay for them
I just bought a domain that was listed at $1500 on sedo.com
I offered $100
He came back at $1150
I came back at $200
He came back at $450 FINAL OFFER
I came back at $275 FINAL OFFER!
He accepted.
The funny thing is that the domain was worth $500 to me, BUT when I saw how far he was willing to drop his pants, I decided to go low ball on my final offer and risk not getting the domain.
Actually, I really KNEW he was going to take it ... just felt it!
Anyway, it's probably not worth $275 to most anybody here, but I'll make it worth a whole lot more very shortly