The payoffs of the jackpot and the other prizes are the responsibility and are under the control of the individual states. Even though I'm playing for the same jackpot, if I buy my ticket in Michigan, I can't cash it in Ohio. The only money pooled in Mega Millions is the percentage of ticket sales that goes into the jackpot and it's exactly the same for each Mega Millions state.
All secondary prizes are paid from the individual state prize pools so the payoff amounts are the prerogative each state. Matching 5 + 0 on Tuesday's drawing paid $250,000 in Ohio but paid $697,476 in California.
Florida would be a nice addition to either Mega Millions or Powerball but the state lottery commission has to determine the effect it would have on current Florida games.