I also think that engineers would be paid much better than product managers in such an organization, given the higher demand for engineering skills (there should be more engineers than product managers on any given team) and a smaller pool of potential hires.
The tradeoff is this:
1) PMs get broader visibility across the org, which tends to result in faster promotions into management for "good" PMs.
2) PMs atrophy technical skills and become more dependent on the larger organization (they acquire more firm-specific skills in econ talk) than do equivalent developers.
So, sometimes if you like your company and want to advance quicker, you will be willing to trade away some industry or general skills for firm-specific skills to get faster promotions or more power.
(in most companies) more money, power, autonomy. Except in very early stage startups, it is the rare developer who has more of any of this than even the lowliest PM. e.g: I think Vic Gundotra makes more money, and has more power at Google than most (all?) engineers there.