So...
OpenAI's business model may or may not represent a long term business model. ATT, it just the simplest commercial model, and it happened to work for them given all the excitement and a $20 price point that takes advantage of that.
The current "market for ai" is a sprout. It's form doesn't tell you much about the form of the eventual plant.
I don't think the most ambitious VC investments are thought of in concrete market share terms. They are just assuming/betting that an extremely large "AI market" will exist in the future, and are trying to invest in companies that will be in position to dominate that market.
For all they know, their bets could pay off by dominating therapy, entertainment, personal assistance or managing some esoteric aspect of bureaucracy. It's all quite ethereal, at this point.
It's potentially way bigger than that. AI doesn't have to be the product itself.
Fundamentally, when we have full AGI/ASI and also the ability to produce robots with human level dexterity and mobility, one would have control over an endless pool of workers (worker replacements) with any skillset you require.
If you rent that "workforce" out, the customer would rake in most of the profit.
But if you use that workforce to replace all/most of the employees in the companies you control directly, most of the profit would go to you.
This may even go beyond economic profit. At some point, it could translate to physical power. If you have a fleet 50 million robots that has the capability to do anything from carpentry to operating as riot police, you may even have the ability to take physical control of a country or territory by force.
And:
power >= money