It's not a large prize though.
OpenAI spent many multiples of the prize money in just a few days to get there and even if one solves a problem in the traditional way, that person is most likely already an accomplished professor at a reputable university where a million dollars doesn't mean as much as the eternal fame that comes with it.
It's definitely not a large prize for OpenAI, but actually IIRC they only spend a few hundred thousand dollars.
It is a large prize if you're just an academic.