I saw this thread and was thinking....don't feed the troll, don't feed the troll. The sky is green and the grass is blue, please disprove in less than 1000 words.
I paid a fair amount for my GTV after looking at loads of them including a couple highlighted in this thread. An average man on the street doesn't want a GTV v6. They are costly to run and anything but practical and because buyers are few and far between, any trader other than specialised dealer, doesn't want his money tied up for that long before he sells it, this is why 'book' prices are low.
Have a look on autotrader/ebay etc and see how many GTV v6's are for sale at any one time, less than 10 in the whole country usually. As the numbers of good ones become fewer due to neglect, prices will inevitably rise, it's not rocket science.