I was shocked to learn that the participation fee for a large annual European conference almost didn't change when the host country changed from one of the most expensive Western European countries to one of the most inexpensive Eastern European countries. I couldn't see any explanation other than the organizers making a huge profit, given that the number of participants was a few hundred and the participation fee was about 500 Euro per participant.
So, my question is: How common is it for conference organizers in academia (that is, the responsible institution and/or members of the local organizing committee) to derive a monetary profit by deliberately charging a too high participation fee and pocketing the difference between the collected participation fee and actual expenses and/or by getting a kickback from the venue or a hotel?
I'm asking about making an unduly good profit that is clearly not commensurate with the time and effort spent by the organizers - say, a profit at least a few times larger than what the time spent by the organizers is worth according to their paying rate at their institution.
To put it simply, do conference organizers in academia make good money?