After I placed the order for my Tesla, I was provided with a Motor Vehicle Purchase Agreement (There is a link in my Tesla Account called Order Agreement): That document states the following:
Until your Custom Ordered Vehicle enters into production or is matched to a vehicle, as applicable, you may make changes to your Vehicle Configuration. If you make changes to your order, you may be subject to potential price increases for any pricing adjustments made since your original Order Date.
Until your Custom Ordered Vehicle enters into production or is matched to a vehicle, as applicable, you may make changes to your Vehicle Configuration. If you make changes to your order, you may be subject to potential price increases for any pricing adjustments made since your original Order Date.