Let's try a thought experiment. It's not subsidized. It's not "worth" the tens of times it costs if accessed through API. Let's drop the subsidy word, they're selling you a product, and they're trying to sell other people a similar product at 30x the price with some excuses. If either (or both) turns out to be unsustainable, they haven't been subsidizing you, they just had a crap business model (or a perfectly good one, if the goal was an inflated valuation, an IPO and then a crash once the losses are socialized).

They might raise the price, but I don't think they will ever get rid of the $20 tier. It is way too consumer friendly and likely has the highest percentage of users that aren't abusing their quota limits. A layperson will be extremely hard pressed to create an API key, know what to do with it, put money in their account. People want an easy subscription.