deggis, "couple of millions" (whatever that really means) for P1/P2 seems a little bit low. I've asked on another forum and a guy said that "according to his sources" Chamberlain Synergy has an annual budget of ~$40-50M, which is up there with the Peugeot ($150/3 years). Of course, I don't know how reliable these numbers are. It seems like a lot of money for what is basically a customer chassis that isn't even close to the front runners.
In this year's 24h LeMans broadcast on Speed the commentators mentioned that the Aston Martin team would like to return to ALMS, but can't find the funding. Considering their past successes and the brand cachet, I would venture a guess that it costs quite a bit to run in ALMS, even in a GT1 car.
Thanks for your links!