Re:
As a moderator I'm probably in a position to raise a couple of points regarding forum etiquette.
Firstly, Retrobike is a fairly diverse community of highly knowledgeable and very enthusiastic collectors, restorers, riders and bike geeks.
We offer free advice and opinions.
The valuation section sometimes gets people giving valuations. Sometimes it doesn't. But they are always free valuations.
If you want an 'expert' valuation you usually have to pay an 'expert'.
In this instance the first valuation started with "I'm not a leading authority on GTs". To complain about what is perceived to be a low number seems a little churlish given that it's potential inaccuracy had already been acknowledged...
The fact is, by posting up on the forum you have given your bike a lot of free exposure. If you are indeed getting offers of $750 (£500) then I suggest you take them.
I'm no expert, but if you are getting those sort of offers for that bike then I need to start selling some of my bikes while the market is red hot.