Great question. Unfortunately, I doubt you will get a detailed answer about valuation in this thread since already, there is a disregard about something called 'competition' and other unknowns in the market that many commenters have totally ignored other than they know that SpaceX is run by Elon Musk and would immediately buy shares on IPO day, whenever that happens.

One certainty is that those private investors involved are already set to take some of their profits on IPO day which means they will dump some of the shares to catch out the retail investors immediately rushing to purchase SpaceX shares at very high prices.

Not saying you shouldn't buy at all, but keep in mind that institutional investors are there to make money and will get their return on investment and can/will manipulate the stock to make even more.