Well past boss 25 the hp on the boss is inline with a bit above average stat .
Past 35 , it is creepy how much more the boss needs to be hit , to even ultilise the money options .
Let say if you are not in the top 5% of stats way above your level , don't think next event kill 50 bosses is even feasible .
Considering they hit the switch on day 1 to make stuff easier (was stuck at 7 bosses with 18 hits way above average for a new account) .
Let simply say it is up to them how they want to run this event again.
long and short version the middlefinger if you are average stats to even complete the event ,
free stats if you belong to the top 5% (but then again those uncommon and common don't do a thing )
So all in all it is fair since everybody gains stats boost , the free player the most !
The money spender just need to calculate . if the investment is worthwhile or not.
And the top players get it for free !