Rarety Andy, rarely!
I based the price on a trade 3.2GTV I saw for sale recently that sold within a month.
It was in good condition and mileage was lowish, 40k miles from memory.
That was for a GTV 3.2 and ok, it was trade, but they made a couple of hundred 3.2 GTV whereas only 37 3.2 Spiders were made of which few low mileage clean examples remain.
You just never see 3.2 Spiders come up for sale I saw one about 6 years ago, blue, low mileage with the optional hard top. It was up for around £9k from memory and I enquired but it sold pretty much the same day!
There was also one in Spain/Portugal a couple of years ago, average mileage, around £11k but it was LHD so it doesnt really count.
I have also seen some leggy examples at around the same money I am asking.
Monza Sport had P3.2 GTV up for the £11k mark (I know of the owner), had done 130k miles, was on its 3rd engine but TBF was in good condition. The owner, in the end, couldn't part with it and removed it from sale even though he had a buyer and price agreed.
I have kept a very close eye on the GTV/Spider 3.2 market over the past 10 years.