It's not all the cards but companies (recruiters) usually have information asymmetry on their candidates. Sites like levels.fyi are a good remedy, with the right info and counteroffers you can negotiate salaries/sign-on bonuses up by pretty large amounts.
I tried this in West Norway recently, being as firm in the negotiation tactics as possible. Didn't yield higher offers at all! So that tells me the market here is actually not nearly as competitive as all the consulting companies try to make people believe.
In other words, the success of this strategy is market-dependent, but it certainly seems to have a huge effect in SV.
For the employer that means hiring the next best candidate, or not hiring anyone for that position. For you it means taking the next best offer, or staying at your old place etc.
The concept is closely linked to opportunity costs.
In general, you can negotiate an agreement only between your BATNA and their BATNA.
(Part of interviewing in batches is that you can credibly present that your BATNA is very high. So you can be tough in negotiations.)
Yep, I'm aware of this and use it. I guess in these terms, my claim is that the BATNA of most companies here is actually that they have all the engineers they need at low cost. But are presenting publicly that they have a shortage and more people should become engineers, so that they can get them even cheaper.
It might be competitive in the other direction: too many engineers, not enough opportunities. Then it becomes a bidding war to see who will accept the least pay.
Just a few years ago many large silicon valley employers (including some companies on the above list) were part of an illegal anti-poaching agreement and were sued and settled with the DOJ for it. Just because engineers get paid a lot doesn't mean their employers aren't scummy.
What makes you think companies hold all the cards? Especially in tech.