The difference between schmucks like us taking that beating for that price and Punk is that the embarrassment factor for Punk is significantly higher than any of us. None of us would be embarrassed getting our ass handed to us by a pro fighter. A famous person doing that takes more of a hit in that department and that can impact some revenue streams if it's bad enough.
I think people are also missing all the work and time invested prior to this. He's not doing this if he wasn't successful throughout the rest of his life too. Easy to looks at this as 2 minutes and change of work but really it's the accumulation of over 20 years of work.