I think this sumarizes your point of view quite good, so I choose to focus on it:
an example is paul wesphal who was the coach of the phoenix suns, when the suns didnt want his services anymore, he choose to coach a high school team i think and he transform that team from a mediocre to a team that swept their conference.
the school wasnt known that much, but he did his job
but when they reach the nationals or since they qualified for the higher league the first game they lose and wasnt able to advance further
now this is what i mean, its not about guaranteeing anything but show some damn results of hiring someone good at all.
If I understood the numbers you put out on your previous example, the PR10 actually showed some results for you, however those results where not good enough to finance his extra salary. I do not see why this should be reasonable.
As an example a swedish first division team, M7 Borås, hired Magic Johnson for a season. Of course this was a few years after his career, because during his hey days the club would have gone in bacruptcy just paying the salary for one day. Anyway, even though he was not even close his best, but still he was better then the competition in the swedish first division.
And how did it end? Well, Borås whent in to bacruptcy, as he turned out to be way too expensive despite adding a lot of publicity not to say increased attendance.
Lesson learned: Not even in the highest divisions (in Sweden) it pays off to have a player that isn't even close to the best available player in the world. The same goes for the most expensive PR guy, doctor, coach, etc. Thus, i think it makes sense that in BB to you have to judge if your team is up to the level where the most expensive guy actully pays off.