They have probably between 5-10k listeners, so if 500 listeners pay, thats still $10,000, which while not being a full time salary for two people, is quite a bit of money for essentially talking for an hour and change a week. It's at the least a good supplement.
I think that they will get more than 10% though. Jesse asks for donations which is I can't see people caring about as much. Also, his show is the kind of show that gets the more casual listener.
As for what it portends for content on the future, it seems like every podcast that I've listened to either begins charging or making money in some way or ends up petering out.