The thing about exping over profitting at lower levels now it is quite simple. In order for a character to pay his premmium, he needs to make roughly 18k / h and use all the stamina available within those 30 days.

So what is the problem? That making 10k / h is going to pay you half of his premmium, but you're going to be leveling up really slowly if you compare it to higher exp rate spawns. If you focus on getting as much experience as you can these months (making an investment) In the long term all of them will be able to make more than 18k / h of profit and they'll all be able to pay the premmium by their selves without you having to put any money into it. But if you continue for months making really slow exp and 10k / h profit, you'll actually even be losing money in premmiums in the long term.