The fine was for one location. I imagine it put a dent in their p&l. Likely would've been bigger if they settled on multiple locations.
At the very least, it's a lot more money than they made renting wi-fi access during the event in question. Therefore, this behavior is unprofitable and will stop.
It's also enough to get the people who decided to do this fired.
It'd be about break-even if they have a convention each week, and get 25 exhibitors pay $500 each. So if they had a lot of exhibitors they convinced to pay, they could have easily made a profit after the fine.