How do some people on Mafia Wars have extremely high levels like 700 and 750

People used to be able to do this by posting bounties on themselves, and then constantly healing while people attack them to try and claim the bounty. If you do this when you're around level 50 or 60 then you gain tons of experience really fast because so many people lose fights to you. They fixed this though, so you can no longer gain experience from defending against attacks while you have a bounty.

But you will only get max 50 Experience from a hitlist. and you will get -6 when snuffed. Or you can make you character jobber full of energy and get level fast