Look at it this way. Elon donated his Tesla to SpaceX the company so that they could make history together. They even lended their test flight to the Ark foundation in order to send a datadisk out into the cosmos much like they did on the Voyager space craft, another incredible moment in human history. They included a plaque with the names of all the people who had worked to make it possible, then they made some cool pop culture references, and some extra marketing with the spacesuit. Also, it was an idea voted for by the internet. Elon was sitting backseat for the presentation, and let the whole team take the glory.

This was a monumental moment in space travel, and something that will forward the human race ever slightly forward. That is more important than a silly sports car.

Elon reinvested the money he makes each time into companies that will make the world a better place (EV, solar, space flight). Taking huge risks each time.

He isn't building himself a skyscraper in Dubai, he isn't boasting about which new Ferrari he bought on instagram. If you want to see egregious and vain uses of wealth, see a single red carpet show, or a popular music video. Some of those people have single pieces of jewelry worth more than that car.

The car was already made ages ago anyway. If you had an issue with Elon buying (note, partly funding and then building the company that built) a sports car, maybe you should have worried about it then.

PS, I am not a rich geek and I could not afford a car like that. I am just a regular geek.