Yes, the used car market is wacky right now. I saw somewhere that the 'used car price index' is at an all time high. And I just 'overpaid' for my '06 Exige that probably would have sold for less last year based on the stuff I'm reading online.
Also, keep in mind that any car that has a very limited production run also does not have a fair number of sales comparisons. Because of this, KBB doesn't even put a value on them and you will see them selling for a wide range of prices.
'07 Exige S - my final answer is get it for $40k or less and you have done well.