If I remember correctly it was 10m for levels 50-60. Then 15m for levels 60-70. So just a guess but 80s should be 25m
"I guess there is no change in the mechanism after all." Liam chuckled and stood up. "200 mana cores, 20 item drops, 5 weapon drops, and about 50,000 experience points." Tallying the total gains, he entered the dark passageway which led upstairs. "Time to go to the next floor."