I do not own any Comm figures (though I might break down for the 2-packs instead of their vastly more expensive vintage brethren) but from what other Orgers have posted, they are definitely different. I heard that Mattel long ago destroyed the original molds so they had to cast new molds from vintage figures! This meant the Comm figures were slightly different. I know the facepaint on many of them is noticably different.
As for $$$ for a full vintage collection - do you mean figures alone or figures/vehicles/beasts/playsets/etc? I'm guessing $10,000 minimum for everything, maybe more. Others here would know better than I would.
In either case, best of luck!