Y'see, I don't understand the attitude of dealers like this.
He's offered you £1000 for your Thundercat, which you're not happy with, but will come down £500 quid on the price of the 996. This makes you think you're losing money on the trade-in of your bike and you're not really bothered about the price of the 996 because that's what you want and you wouldn't ask if you weren't interested in it...
Now, if it was me, I would have said:
"Tell you what, I'll give you £1500 quid for your Thundercat. It's a bit more than what we'd normally give but I reckon I'd have no trouble selling it on again. Now, let me just get the keys for the 996 and you can take it for a test ride."
See what happened there? You now think you're getting a fair deal for your Thundercat because it's not far off what you've already been offered, but you're far too excited waiting for the keys to take the 996 out on a test ride that you didn't notice there was no money knocked off the price of the 996.
What it comes down to is that you're paying the same amount of money but it was put across as if you're getting the better end of the deal.
Do the sums to come out with a final figure and if you're happy with that then take the deal. Don't think about getting a price for your bike and a price for the new one, think about the total difference - you might be surprised that it works out as a good deal even if they didn't sell it right!
I don't know ... blinking amateur salesmen!