It is absolutely stupid. This is, money wise, the biggest fight of their of their careers. Mayweather knew this in 2009, and hasn't forgotten it. I believe the split this time is 60/40 and that is likely going to be over $150 million for each. A $40 million flat fee in 2011 (before Pac fell off) would have been highway robbery and it makes sense they declined it, especially considering Pac had a very good chance of winning IMO. I mean, I don't fault Mayweather's team for asking for that (since, it would have been great for them), but they couldn't have possibly expected this to be the case.
I really feel whoever loses this fight retires. Pac simply because he's mostly done (you don't see the same guy that destroyed De La Hoya in the ring anymore) and Mayweather because he has nothing left to prove. He made his millions and can get out having lost to one of the best fighters of the past 20+ years while beating nearly everyone else.