You have to get the coins, and the fastest way is to do the 2 one time quests then the repeatable fighting quest. Same goes for the 20,000 coins where you get 2 new one time quests after turning in the first 10,000. Takes a bit more time than previous dungeons if you're rushing, but each coin checkpoint can be done in about a week for each if not a couple days shorter than that.
If you don't know about those quests, yeah that would take like 3 in game weeks for each if not longer.