There are a lot of companies right now letting people leave who asked for pay rises only to find that not only is it going to cost them 10k to hire someone new but that person will be 30% more than the old employee even asked for and will be starting from scratch.

I wish there was more data on the "from scratch" bit. I just cannot believe that companies are willing to let experienced devs who know your system and have proven that they can ship just walk out the door with all that value simply because you won't pay them more. It is a ubiquitous problem and my bosses have shared this view. My current firm is the only place that has proactively increased compensation, and guess what, the other ICs I started with six years ago are still with the team.

The upside is that the old employee now got a 10k raise.

However, many companies will eat the cost, because once you improve one person's condition all the rest start asking for it as well. Some managers like sending the message that workers are disposable and will be disposed of if they make trouble.

I'm sure they exist, but I've not encountered any. Most managers are there to manage, not intimidate.

I believe it. But for a lot of companies the standard playbook is everyone is replaceable and they probably wouldn't even consider meaningful change unless attrition hits a certain percent. They'd rather cut a new hire a fresh load of RSUs than refresh you to keep you from looking around.

Varies by company, but IME, bringing issues of pay and stuff up are often hit with the standard "we consider raises in November" or whatever arbitrary time period they've chosen. Then they're shocked when people leave.