Acquihires are more about hiring functioning teams composed of engineers and executives who are used to working with each other. That's a lot more expensive to build than just the salaries; and you can generally take that team and throw them at a problem with a reasonable expectation they'll accomplish something.

Also, there's generally some amount of IP and customer data involved as well.

"you can generally take that team and throw them at a problem with a reasonable expectation they'll accomplish something"

For about 6 months to a year, after which time most of them have left, or have gone into "waiting for the golden handcuffs to come off" zombie-worker mode on a project they have no inherent interest in.

Totally anecdotal but the couple of acquihires I've seen from the inside have gone like this and it seems to be the natural state of them based on what I've heard second-hand from others.

I agree with this based on the 20 or so people I've known to go through this process to join a large company (amazon, google, etc). I've heard first-hand accounts of people even re-negotiating deals just to get out of the golden handcuffs they thought they could tolerate but couldn't. I understand this sounds a bit hoaky and I would love to give names and companies here, but obviously can't.

Agreed; they tend not to be great deals for the acquiring companies long-term. But short term you can rally that team to build something else, and your likelihood of finding the mythical 10x developer (or manager) is statistically higher in a startup that successfully launched a product in a compressed time frame (even if the market didn't work out for them).

Any acquisition involves a lot of turnover. Guaranteed that this turnover is built into the models they use when evaluating acquihires. Consider how expensive most company's talent acquisition costs are though (upwards of $100k+ per candidate hired for top talent) and it starts to make sense.