Powerhour potion. Nonsaveable, personal and purchaseable only
from certain shop, one potion/customer/boot. Price would be
counted from your lvl(/age/whatever suitable).

calculate cost from Exp Totals, i think this is one of the best idea's ever on
how to maybe fix some balance issues and to stop people from whining cause
they lost there power hour for the day.

In theory, theory and practice are the same, but in practice, theyre not.