If you're operating a company with real customers and real cash flow at any kind of real scale, and you suffer a serious breach, figure $50,000-$60,000 is table stakes for getting that breach resolved.
The intuition you need, to price these things out, is that once an attacker obtains unexpected unauthorized access to a system, the very next thing they do (and, in this case, the very next thing they tried to do --- much to Keys chagrin) is extend and persist access. Which means that if you're resolving a breach, you have to re-assess every system that the attackers got unexpected access to and verify that they didn't (a) implant something that will restore access in the future or (b) uncover some latent vulnerability that would allow them to do that.
Nobody reliably assesses internal systems (those systems you get unexpected access to once you successfully obtain unauthorized access). Nobody. An attacker gets behind the login prompt on a CMS you've deployed? You probably need to re-assess the whole CMS, because a big chunk of your security for that CMS probably relied on the idea that attackers don't know and can't reach all the URL endpoints behind the login prompt. The attacker gets code execution somehow? Now they're on your internal network, and the same goes for every system on the internal network.
It adds up fast. And your insurance company will (a) demand that you pay it, and (b) shortlist your DFIR vendors for you.
Not fun times.
[EDIT:] I see you've added some material that explains why investigations cost more. That seems reasonable, but in many cases attackers are not within the reach of prosecution. If we allow firms to blame the "hacker" for needing to investigate how bad their security is, ISTM we're letting them shift the blame to parties who can't actually fix their problems.
Meanwhile: they clearly can't just revert the web page. Keys gave a hacker group a login for a web application. How, exactly, does Trib Corp know how much damage the hacker group did to the server? There needs to be an investigation, and the norm is that the investigation should be done by a third party.
Meanwhile, there's a principle in the law that you take the victim as they come. In US tort law, it's called "the eggshell skull rule". It means if you hit someone over the head with a book or something and unexpectedly fracture their skull because it turns out to have been as thin as an eggshell, you are still responsible for the damage you caused.
If you find out that someone's been coming into your house when you're not there for a few weeks, but you're not entirely sure how, you don't just change your key, you also check all your windows, possibly fix the latch or replace the window on any that are broken, etc.
The cost should generally be limited to the actual damage done by the hacker, rather than include things that the company should have been doing anyway.
After someone uses an open window to obtain entry, does that mean that they can be charged with the cost of locating and auditing every copy of every physical key to the premises, on the basis that they could have found one and stolen it while they were in the building?
