The fad seems to be dying down a bit, at least in our area. Several years ago I was working for a large national insurance carrier located in my area, and many of the local food trucks would regularly park outside there for lunch service - which made sense given how many employees worked there. So I got a little carried away with eating from them for lunch several times a week, since it was kind of a treat at first to have them around so often. But it did start to add up over time, since the food trucks were generally more expensive than what you would even pay going to a fast food drive thru, or even buying some prepared food at the grocery store.
They were getting a bit carried away with their prices, riding high on the popularity of the whole fad, and they really weren't in line with the quality of the food being served. Not to mention it simply wasn't economically practical to eat from them several times a week due to what they were charging. If I'm already paying like $7-$8 for a sandwich, then don't charge me another $4 for a side of fries to go along with it. One of the trucks in particular was charging $4 a piece for a side of what was essentially plain old frozen tater tots, tossed with a little dried rosemary to make them "gourmet".
They're fun from time to time, especially in the summer months when I'm hanging out with friends downtown, and want to grab a quick bite to eat without waiting to be seated in a restaurant. But I'm a bit pickier these days over what's really worth it in terms of value for the money.