Really, you are claiming that if a company raised $570M and sold for $3B, the common shareholders will get screwed? Do you have some information we don't? The publicly reported valuation at the last funding round was $1.4B. Those would have to be some impossibly harsh terms to not leave well over $1B to the common shareholders.
The price in these "the business model didn't work so let's save the investors and sell" type deals is primarily driven by paying off the early investors. Term sheets typically say these investors make a decent return before anyone else gets paid.
Conversation at the deal table is usually something like "we need X valuation to meet our term sheet with investors so the founders and a few others get paid." The rescue buyer generally doesn't care about what the employees get, in fact it's very much in the buyers interest that the employees don't get too much.
In other words the size of the valuation being bounced around is likely not driven by the value of assets for shareholders but rather the size of the contractual hole in the ground that founders dug with their investors... to escape that hole $X is needed.
> "Those would have to be some impossibly harsh terms"
Harsh terms yes, but not uncommon.
Preferred shares are common for investors that pay out at a multiple of the common shares, so in an exit the preferred pool can be paid at a dramatically higher rate than common shares.
Funding often also comes with guarantees on return - i.e., if the exit price is below a threshold, the investor gets a guaranteed minimum return before other are paid. This works out for the company if it's a smashing success (the upside is also capped) but can wipe out common shareholders if the company sells for anything less than stratospheric valuations.
This should be a lesson to anyone thinking about working for a startup: a company raised $570M and sold for $3B, and in all likelihood the employees will receive very little from this sale.
In the modern startup fundraising scene, and the way startup equity is structured for employees, if your company exits for anything less than a mind-boggling headline-making valuation, you are almost certainly receiving little to nothing.
I feel you just haven't proved your claim given the numbers. Even if the last round's investors were guaranteed a 3x return, that only takes up $1B of this $3B.
Granted, I don't think many engineers are making out with seven figures here, but they should be making whatever their shares were supposed to be worth at the most recent valuation. That's if they joined after the last funding round, more if they joined earlier.
