TL;DR - there is surprisingly little money in politics. Even the "low billionaires" like Elon Musk (who has like 10 times less money than Gates, Buffet, Bezos, Bloomberg) could easily overspend all other candidates together.

Also, corporations spend surprisingly little, like, a rounding error compared to how much they could spend.

And there's a cynical response that they are gaining influence in other ways, but it's not like we usually model corporations as agents of great restraint, so why wouldn't they also do way more political spending?

Why would they spend more? They're already getting the outcomes they want.

Why do they lobby as much as they do if they’re getting everything they want?

They are getting what they want because they lobby as much as they do, not in spite of them.

That sounds like a just so story to me, though. They could spend way more on lobbying, and get more - more subsidies, more tax incentives, etc. but they don't. It seems very unlikely to me that they get everything they could possibly want for such a tiny fraction of what they could spend, given that most everything at the Fortune 500 level is a race to the bottom.

FYI, Elon Musk is worth dozens of billions. Not sure I'd call that "low". [0]

[0] - https://www.forbes.com/profile/elon-musk/#44fcf3a7999b

I heavily discount the market value of SpaceX, which is a private company (recent events have taught us that such thinking is prudent...).

To be fair, at least one of those notional "dozens of billions" came in just the last few weeks.