Wanted to add color to this interesting phenomenon. Used Teslas are not really cheaper than new Teslas - if you buy from the same dealership, new cars are still priced higher than used cars at a significant margin. The difference between buying a used car and ordering a new car is in the expected value of money. With inflation and with wait time of 6 months, a dollar today is worth perhaps a dollar and 5 cents at delivery. So the same used car that's worth 50k today is worth 52.5k by the time you take delivery of the new car, just from present value calculations alone.
Add to this 4 more things: gas savings (if a month of driving an EV saves you $300 dollars for example, getting a Tesla 6 months earlier nets you $2k), and the prior inspections by the previous owner and by the dealership (presumably any possible issues have been uncovered and fixed), the slow depreciation of the Model 3 (due to a rise in demand and due to its supposed lifespan of 1 million miles), and the ongoing general lack of car supply, and you get this odd used car prices for the model.