I had the fortune of working in a company where the direct monetary impact of a bug was easy to calculate like this. One user produces €100 / hour. If the bug cause a service outage for 1 user for 1 hour the direct cost is €100. This was very liberating as we had very constructive discussions about the priority of bugs and also the efficiency of the testing process.
But after that one problem with all these systems are that all bugs are not equal. You cannot discuss only the number of bugs. A typo on a manual page that only 1 in 100 users visit is not the same a the interest calculation is of by 0.1%. And then you also have the good will / bad will as in. 100 minor bugs will individually not register as a “big problem” but working in a service with 100 minor bugs decreases your trust in the product and the brand which might cause you to cancel the service or chose a different product.
But as per the Black Swan project, the value might not necessarily lie in the correctness of the calculation but in the insights that comes from the process of the calculation, and it still might be useful to decide on incorrect monetary values instead of abstract numbers.
Currently we do not have error budget, but checkpoints. “No bugs that cause beyond this point.”