It's like many startups: spend other people's money by finding investors.

It's a bit of a semantic game, but investing != spending. Paying someone's salary is not an investment in that you don't get money back from that person, you get something of value hopefully, but not a monetary return from them. Investing in a movie or a startup has an expectation of a monetary return, so the investment is not "spent" (relevant synonyms: exhausted, consumed, depleted) by the investor.

Then whoever is actually making the movie, versus investing in it, is the one spending money. But it's not their money, it's the producers' money.