SpaceX is trying to develop a new kind of rocket, with insane upfront R&D costs.

MoviePass is trying to sell movie tickets for less than they paid for them.

I don't think those are similar at all.

This is facially true. But I don't think MoviePass would describe their service this way. They would say they are gathering unprecedented amounts of personal data about movie preferences, which can be worth millions to movie studios and TV production companies that want to know what type of content will attract viewers. Framed this way, it is more understandable that they would need to burn cash in order to get the ball rolling on data collection.

Still, it's not rocket science and probably could have been done much more cheaply (just offering subscription coupons or something).

is said personal data harvesting going to be worth multiple dollars per movie somebody watches?

somehow i doubt it.

SpaceX lost money on R&D, they didnt lose money on the launch itself. i.e. every actual customer increased the money in their bank account.