We have a collective 25 years of negotiating experience and have successfully done hundreds of deals. We started in the entertainment industry negotiating deals and contracts for musicians and have been doing so for senior tech talent for the last 5+ years. We don't want to imply that you are not qualified to negotiate, we are simply offering our expertise to anyone who might find it useful. You can find much more info here on our FAQ page or feel free to contact me directly!
Sure - we've been doing these types of negotiations for senior and director-level (even CTO-level) engineers for over 5 years now. We have helped engineers negotiate employment packages with Facebook, Google, Stripe, HSBC, Apple, Salesforce, Instacart, FireEye, Attune, Palo Alto Networks, and many more.
While I don't have a hard statistic/number for you (we are working on putting those numbers together now) our most recent client got over a 100% increase over the initial offer. We also had a client that got so much more than they were initially offered that their future boss also got a raise because the company had to rethink the pay structure of the entire division.
I understand if it's hard to calculate the median. But what's the minimum increase?
Some of the companies you mention try hard to make the initial offer compelling/fair (e.g. slightly above max of {current compensation, competing offer, target compensation for level}), so I'd assume that sometimes they simply won't budge beyond that, as they feel that they've taken into account all relevant info before making the offer.
https://10xagentondemand.com/faq/