It seems fairly straight forwards to me... you pay the other 17 people in your group 1 mil each to do ADL with you. Assuming that you farm your own pop set before-hand, and can then farm another pop set with each group and kill 2 ADLs within that 2 hour frame; it's 170 mil for the 1st stage to a 99 relic. This is assuming he averages 1 UM per fight.

The fewer number of people that you can kill him with, or the more ADLs you can kill per run = the less it will cost you.