Totals are not cumulative. You need to have 50,000 at one time.
The easiest way is to do the following:
1. Travel to Everlight temple
2. Go up the curved stairs and stand on the switch to open the secret room.
3. Go back down past the teleport up the big stairs and onto the ledge along the side.
4. There are 3 chests in the middle of this ledge, and 2 on the end.
5. Go in secret room and smash all the chests. You'll have about 1300 gold per round.
6. Run back along the ledge and go straight out of the area.
7. Turn round and re-enter the previous area, repeat from step 2.
It takes about 40 rounds to complete if starting from scratch.