So about $4,000.00 divided amongst how many players?
I'm kind of just pulling this out of my ass here but if I had to guess I'd say probably fewer than 25 players would account for 70%+ of total overcharged rake. There are not a huge number of regs putting in volume.
It's also possible, 2 or 3 guys could be making up 70% of total overrake. Any HU Bum hunter could of easily put in 40+ hours at the mid-high HU Cash games over the course of 5 or 6 weeks. This would ad up to 5BTC + stolen from them.
I think attempting to pick a single number won't really be as meaningful as trying to determine a realistic range of what was taken.
The problem is that you are the only one doing anything about it and the people that were scammed don't do anything. I was not playing enough here at that time and less now, to get upset about very little money.