Lets say you have an average of 2000 for every convention. They say they will have it filled for 40 weekends. That means 80,000 visitors. That's about 26 700 families. Knowing that the conventions are now one day, we can assume that the average family will spend about 400$. Hotel, food, gaz, etc. That's $10.7 million/year. Considering that many will simply drive back and forth while making their own lunches, and some may not even purchase gas in the town itself, we can easily knock off 2 million out of that. So, a reasonable estimate is probably 8.5 millions per year.
I have no idea how they can boost that up to a 165 Million per year.