I mean it is not the end of the world but you are paying for a brand new car not a demo. Why should you pay the same for your car with 272 miles as I did for mine with 4 miles? It is like brand new pair of sneakers vs. a pair that 30-40 people tried on and walked around in.
If the average customer test drive is 5 miles or so that could mean 50 test drives? Demos at traditional car dealerships usually get some form of extra discount. To me the extra 270 miles it is worth ~$500 in accessories at the Tesla store, which would be good for a Wall Connector, Trunk mat, etc. You will never know unless you ask for more discount.