The Monopoly of the Bumper Dumper

A student writes that his family was fortunate to have the Bumper Dumper, produced by the Uncle Booger Company, attached to their SUV on a recent trip.
This device — essentially a toilet seat attached to the back of the car — has substitutes, like any other monopolized product: nearby gas stations, the roadside, etc., although the former is infrequently available in isolated areas, and the latter probably doesn’t provide the same high-quality experience.
The company charges $70 — a high price, but the patent on the unique hitch attachment allows it to charge this price and still sell. I expect the monopoly to disappear when the patent expires; but for now, it allows this innovating entrepreneur to earn monopoly profits. Isn’t American ingenuity wonderful?!
(Hat tip: J.W.)