I do not think they are aiming to be cashflow positive now. That might not be possible. Though if it is within range they might want to go for it. Because the stamina needed to win this race is going to be immense. Especially since OpenAI is going hard for scaling up via investor funding, and Google can afford to loose/invest a couple billions annually by diverting from their main revenue sources.

A realistic business plan would be to burn cash for many years (potentially more than a decade), and bank on being able to decrease costs and increase revenue over that time. Investors will be funding that journey.

So it is way too early to tell whether the business plan is unsustainable. For sure the unit economics are going to be different in 5 and 10 years.

Right now is very tough though- since it is basically all early adopter power user types, which spend a lot of compute. Later one probably can expect more casuals, maybe even a significant amount of "gym users" that pay but basically never uses the service. Though OpenAI is currently stronger for casuals, I suspect.

Over the next decade, hardware costs will go down a lot. But they have go find a way to stay alive (and competitive) until then.