A
IMHO -
If a valid company it is worth low to mid £x,xxx...
As it is short, brandable BUT, other alternatives are available for reg. fee...
If an individual, I would say roughly mid £xxx...
Anything higher would probably deter the sale though a drop into sedo auctions may work to your advantage once an offer is in place.
The key to this one is trying to determine who is making the offers...
See if you find out more from email headers.