I don't think it is not entirely impossible to cross that 10GB mark on an average if that is his only connection!
I recently met a bloke(a new recruit) who had an internet plan where the minimum assured speed was "just" 14.4 Mbps and the maximum possible speed was a mediocre 21.1 Mbps, but that came with an astronomical price though(almost equal to his current salary and that too without taxes!).
We actually had a bet whether he would attend a nature's call or phone call! xD
But, he seems like a really likeable guy, he never uses his office computer for his private use.
Sadly, he complains a lot that “this time his ISP outdid his brand new high-end cellphone (maximum possible download speed being “only” 10 Mbps)”.
Still, wondering why is he paying more for something that he really can’t have right now!
In his plan, FAP/FUP is implemented in a slightly different way than it usually is.
Here, the speeds remain at the speeds that was assured (with maximum possible being 21 Mbps) even after crossing a certain limit but a new billing starts where he has to pay per MB.
So yeah, money not being a constrain, that is possible even on a cellphone!