I think I'm mostly with you here, although I wouldn't go so far as to write to the auction winners, but that's because I'm generally too polite.
I have a '69 GTO, and almost NEVER look on Ebay for spare parts for it. They are just too expensive and the competition is too intense. Like you, I like the fact that the '73-'77 GPs are not very popular, and therefore the prices aren't through to roof yet for them or their parts. Sounds like that might be changing, which is a very bad thing.
Luckily, I now have a '78 Lemans to work on and buy parts for. It's no '87 Sunbird, but it is also pretty much a Pontiac orphan that there is no parts scarmble for.
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