Haven’t their prices stayed at $20/m for a while now?

They've published anticipated price increases over coming years. Prices will rise dramatically and steadily to meet revenue targets.

AI doesn’t have much of a moat. People can and will easily switch providers.

Sure but there are only a couple leading providers worth considering for coding at least, and there will be consolidation once investment pulls back. They may find a way to collude on raising prices.

Where switching will be easier is with casual chat users plus API consumers that are already using substandard models for cost efficiency. But there will also always be a market for state of art quality.

Reinforced today:

As Gemini has gained competitiveness (higher confidence in its output, better reputation), its prices have steadily risen