That's wrong-headed thinking because the original Roadster was a proof-of-concept EV in order to get media publicity and sell the upcoming Model S to original Roadster buyers and their family, friends and co-workers/acquaintances, etc. Not any old publicity would work, it had to be good publicity. If people viewed the Roadster as overly impractical and/or couldn't even get in it for a test drive/ride, it wouldn't have been nearly as effective as it was in getting pre-sales of Model S. Tesla was depending upon those pre-sales in order to go public most profitably. Being seen as the maker of overly impractical cars could have been the difference between reaching critical mass and people losing interest.
The Lotus Elise sold over 10 times as many because it was surprisingly affordable, sold to a much younger sports car crowd (who were not overly concerned with ingress/egress issues), and it sold over a much longer timeframe.
Elon knew that the expense to lower the door sill was peanuts compared to the amount of money they were going to need to raise to take Tesla to the next level. Elon didn't want to take any more risk than he absolutely had to that lack of confidence would lead to failure. He also knew that people who had the kind of money he needed to carry out his plan tended to be older, some of them not in the greatest shape. It was less about selling more Roadsters and more about creating the car maker image he needed. His brilliance was in having the vision to know what to spend money on to make his plan most likely to succeed.