Low mileage though, and it does come with the warranty.
Although we know the car you're looking at is for sale in Texas, we don't actually know who's selling it. This is not so surprising. You see, the McLaren P1 is essentially brand new, with a mere 400 miles on the odometer. The asking price is $1.85 million, a full half million over the $1.3 million that McLaren charged for the car, so it seems very likely that the owner bought the car solely for the purpose of turning around and selling it for a profit.
The makers of exotic cars, and certain brands in particular, tend to really hate it when people do this kind of thing. They build the number of cars they do, sell them for the price they do and sell them to the people they do all for a reason. Ferrari has certainly been known to ban certain individuals for life from ever being able to buy another limited edition car from them for doing this exact thing. So it's no surprise that we don't have a name for this individual. But we're guessing that McLaren could find out if it wanted to. It would just be a question of whether they cared as much as Ferrari does.