Obviously they need more paying users. The entire game in tech is taking advantage of (comparatively)low marginal costs to pay off capex once you corner the market
I do think that's at least part of the strategy. The problem is that we've never seen a single product category so hyped in history, literally trillions of dollars invested. To recoup that, some not so trivial miracles will need to happen.
I think that within 5-10 years most white collar workers around the world will be paying for AI assistants. There are 1.2-1.3 billion such people to sell ai to, so getting more users doesnt really seem like a miracle to me. I do think convincing everyone to use expensive proprietary models instead of open ones hosted cheaply by third parties will be a minor miracle for the AI labs. Definitely not out of the question though.