That's so Texas. Compelled business relationship.
rental companies do that in every state with toll roads
It can be worse than your estimate. I took a rental car through one here over summer and Hertz declared that by incurring a too, that I'd opted into their toll service at $5/day for the length of the rental, plus paying the toll.
On the drive here, Gooch & I drove the Budget truck through some stretch of CO that apparently was a toll road, and I'm just now being asked to pay the toll + $10.