The price is a factor of a great many things. Cost of inference, desire for user growth, market competition, investment recoupment, revenue numbers for S1, tier/rate balancing, etc.

They cannot follow the Uber model because of scale. You could keep getting tens/hundreds of millions from investors, back when there was lots of cash floating around. But you can't keep getting hundreds of billions of dollars. There are only so many dollars. The world is tapped out of private capital. That's why they want an IPO - so retirement and pension funds are forced to buy their shit stock, and feed them more money. But again there is only so many dollars.

Anyway it does not matter. Subscriptions are the most effective way to extract wealth from customers. This has been established so clearly that every business in America now has a subscription. Your fridge, TV, car, hell even car washes, now have subscriptions. Not because they didn't make money from you before, but because it's the ideal way to make even more money off you. There is no reason not to use subscriptions. No AI company in their right mind would end them.

The question of how much value you get from the subscription is different. They have already adjusted both price and rate limit a dozen times. They will keep adjusting it... but the subscriptions are here to stay.