Earlier quoted context omitted.
A classic false comparison: the four experienced security researchers working for multiple months covers 55 issues, not "that one issue". If we're cherry picking a single one, the associated involvement and timeframe drops dramatically, to something much closer to one or two people, tops, over the course of just a few days, tops. That's something a pentesting team can absolutely achieve for far less than $500,000 ove…
There's really 2 options here. One, Apple doesn't employ a pen-testing team currently, which would be nuts, or, two, the pen-testing team couldn't find these bugs, or they'd already be found.
Apple is also huge, and no huge company avoids vulnerabilities; staff as ambitiously as you want, but any disjoint group of competent testers attacking a new target is going to find a disjoint set of bugs.