If Michigan and Florida wanted to spend the extra money, it could be a party run primary.
Primaries are very expensive. Michigan is flat broke. Unless the Democratic Party is willing to spend the dough to finance it, that probably couldn't happen.
If Michigan and Florida don't want to pay for a re-vote, then they shouldn't get any delegates.
Michigan might if its a caucus, though stated before they are flat broke and Florida is laughing at the fact of a re-vote to seat their delegates. So I doubt neither will go for it, and alot of people inside the democratic party wont be happy if the DNC actually went through with it.