It takes an enormous amount of work to find that good engineer in the pool of unemployed workers. This is why big companies pay for sourcers, recruiters, referrals, interviewers, etc. In a typical company, that 1 good hire resulted from looking through hundreds of resumes that didn't cut it for one reason or another.
When a company does an acqhisition, they short circuit all that work, and get a pool of vetted, battle-hardened engineers who are known to work well together. That's worth a lot more than just the engineers' salaries, because there was a lot more than just their salary that went into convincing them to work for the startup.
If they just offered $180K, a number of the employees would turn it down, because they go to work for the intangibles like having good coworkers or working on interesting products, and the only way that Yahoo can bring them on board are to keep those intangible perks intact until they find a way to assimilate them into the mothership.
I call bs. It's honestly insulting to every Yahoo employee to hear this argument that these guys coming to yahoo via a dying start up are worth several multiples.
Your entire post doesn't even touch upon the fact that most of these companies are failed companies. They aren't exactly companies whose talent created a product that was killing it. Just as you give credit to them being a team, you should also discredit to them failing--not as criticism but to be consistent in trying to value them fairly.
There are many teams, particularly in big companies, that fail to do even that.
Many people in the startup world don't understand this, but the vast majority of people in the labor force are not primarily motivated by money. You need to pay them enough to feel like they're not being taken advantage of, but beyond that, they go for work environment, interesting coworkers, challenging projects, and other intangibles. To have any chance at all of hiring them, you need to provide those and not just money.
(Google understands this very well - they explicitly state with their offer that most people who work for Google do not do so for financial gain. They do it because they want to be a part of something great, and have really intelligent coworkers, and be given a flexible and creative work environment. Yahoo has a big challenge matching this, given their current lackluster stable of products, and Marissa's trying to jump-start the virtuous cycle and bring in folks that people would want to work with.)
Yahoo is betting that it wouldn't be able to induce someone to jump ship, but once they have jumped ship, their work environment is "good enough" to keep them. Well, most of them.
It's the same reason why magazines and online services bill by subscription (it's a lot of effort to get someone to subscribe, but much easier to keep them subscribing), and why ISVs bundle a lot of crapware with major platforms (users wouldn't knowingly install their products, but if they're already installed they won't bother to remove them), and why UX designers make the default settings whatever benefits the company most (most users never change the defaults).
But, this is for departments of 6-10 people.
One reason why offering a higher salary is a non-starter, is that, in order to properly level those new employees, you end up having to pay all of your existing engineers more money as well. So, if you increase your existing engineers salary by $30K * 10,000 engineers, you just paid $300 million/year as opposed to paying a one time fee of $70mm.
