part of it is due to the fees, but i think a bigger part for these post trump prices are the limits on trading and the limited number of traders. the number of traders is limited for each market, so a lot of these markets are closed to new investors. when you have no one new who can trade on one side and traders holding losing tickets preferring to wait for resolution rather than sell at a loss on the other - the price isn't going to move much.
that can't be the whole story, however, because there are plenty of markets open that also have crazy pricing. so i think another aspect is that predictit just hasn't resolved most trump markets yet, so traders still have all their money tied up in those markets. i think there is probably a limited number of people that are both interested in betting on politics over the internet but who didn't already put their money down before the election.
all that said, if anyone here still wants to put down money, they could easily put in like 10-20k in markets that are still open and would return 10-11% before fees. can pick up miles/points on the spend too. i recommend it.