Hey SirPaulius,
This would be a hard question to answer because it would depend on your playing style. If you play a lot of hands, you would obviously have more chance of clearing it than if you played like a rock for instance.
We would need to know how much rake you pay per 100h's to be able to work that out, unless we get an answer from a Mansion player who has tried to clear a FDB at NL10.
Regards
Laz