Our race track (horse) does a food truck day each summer and 20 or so trucks come. It's a great event and we find new trucks each year. But they are expensive because the type of event and it's mainly sample size...but worth it.
Most have apps around here and that makes finding them pretty easy. They tend to bounce around as the Chicagoland area is so big.
I like my food trucks cheap! But I'm sure that's some great food at the track and a fun time. In San Diego they stay put for half the day of all day. I was in "bad" neighborhoods but the food was great! Not too many restaurants.
There aren't enough of them around Chicago yet to drive down prices IMO. The demand is huge, but I think largely due to our weather there just isn't that incentive run a truck. Guessing during the winter their business wouldn't be very good.
The prices are better when you find them outside the track, sure the track gets their cut.
I love visiting San Diego. It's one of those places that you visit and wonder why on earth we live in the Midwest and deal with winters. But all our family is here and we see them on a regular basis. Not sure how we would adjust to not seeing everyone.