Does this math work?

[deccan]

Graeme Dice said:
If you expect your mage to be hunting for more than 48 turns, then the demonbred is cheaper.

Heh, how does that work?

Apprentice base cost 150 gold, upkeep 150/15 = 10 per turn
Demonbred base cost 260 gold, upkeep 260/30 = 8.666 per turn.

Purchase price difference = 110 gold
Upkeep price difference = 10 - 8.666 = 1.334

Should take 80 turns to make up the difference, no?