Alternatively, jail the company itself; for some period of time (days? Weeks?) it is unable to conduct any business, run any services, transfer or process any money, etc. Let imprisonment be as potentially life-ruining for a company as it is for the average man.
> At what scale of massive recurring societal harm (Google, Facebook, etc.) should we confiscate all assets [...] and auction off anything.
At the point where criminal fines and civil damages and penalties exceed the value of assets of the firm.
> disband the company
This is less clear. A difference between a juridical and a natural person is that you can't simply swap out the decision-making apparatus of a natural person. You can, if need be, to a juridical person like a corporation, so its not clear what purpose disbanding the firm (whether assets not needed to be obligations are returned or seized—the former being more analogous to the death penalty) serves.
When the penalty becomes larger than the profit from noncompliance. It's simple math: As long as the penalties they are charged cost them less than 30% of all app sale revenue, it makes sense for them to continue to demand the 30% and fight any attempts to make them charge less.
It's why I continue to think the solution is to put CEOs in jail: It changes the equation, and noncompliance is no longer considered a possible option for the business.