I think there is a problem with the xp earned when one up a tower.
From levels 60 (maybe before), building a tower can earn 106k.
With the arrival of 80-85 level towers, it is still 106k with a much larger construction time than tower 60.
To have the last dragon at the max level, it will be necessary to be in the levels 470 …
At 497, you need 600k-700k for a level!
It makes sense to take levels, to have more xp.
But it would also be logical for a tower 85 to yield more xp than a tower 60.
Well it’s my opinion…