Parking tickets

First, are both vehicles yours. Second, were both pics taken at the same time?
Third, not sure what a parking stall is, but why were they expired. Are you prepared to fight it?

Neither were mine, both belonged to people attending the same convention as I. Both were the same day, but different locations and time. Stall = parking spot. Expired = meter has run out. I am thinking they will be paid and not fought because of the cost and time required to fight them.

You're correct. Best you can do is tell the people involved to send a letter of complaint to both the convention organizers and the local Chamber of Commerce. To the organizers, the comment needs to focus on the next venue having ample parking for the event to prevent this from happening. Likewise, in the letter to the Chamber of Commerce, advise that organization that if they expect more convention business, the city needs to provide ample parking for these events. Lastly, I'll assume there are trade magazines for the organization that held the event. A letter to the editor(s) about this type of fleecing may want to make people think twice about where they hold their next convention. I'm not saying they need to provide free parking, but all day parking for a reasonable fee would be beneficial.