You'd be surprised; they only made 20 Reventons and 3 went through the Houston Lamborghini dealership.
It's possible that those three represent the entire US allocation and they all were delivered through one dealership for simplicity. One may have been sold there while the other 2 ended up in distant cities. People with that kind of money don't care if they need to have the car shipped for delivery, it's not like you take a car like that out for a test drive before deciding if you're going to buy it.