There have been some attempts at price guides, but they are misleading at best as the pricing can be affected by so many factors, not the least of which is geography.
If you look at eBay, you are going to skew high on your prices, even if you only look at completed items.
As for a Pole Position cockpit, the big question is "Does it work ?". Pole Position boards are somewhat notorious for their ability to be a total PITA to keep running. The few people that I know with working boardsets keep a ton of spares as a result.
The fact that it is a cockpit may knock the price down a bit as it doesn't come apart nicely and BasementFittage(TM) can be a problem.
I've been offered, and turned down, a couple of non-working PP cockpits (never been offered one that is working), so the big question is "Does it work ?". If yes, it is easier to give a price. If not, then you need to take a look at the likely causes before you can gauge price.