I believe you have to pay tens of thousands of dollars to get your store or attraction on those signs. I used to work at a chain restaurant just off of I-80 when I was in college. (This was in PA). We were not on the sign informing drivers that they could get off and stop at our restaurant. When I asked the GM he said that they wanted a lot of money to be on that sign, like over 50K. Which, in hindsight wasn't that much for the restaurant. However, it was the first time I realized you had to pay to advertise on those signs.