They went from 0 to $5 billion when they were the only game in town. But now the crown of "best model" changes hands every few weeks, from OpenAI to Anthropic to DeepSeek to Google, and that looks likely to be the case for the foreseeable future. People "in the know" have already stopped treating OpenAI as automatically the best, and this knowledge will diffuse to everyone else over time. Without the best model as a moat anymore, there's no reason to expect OpenAI's growth to continue on the trajectory it used to have.
This is actually a SaaS product that has good unit economics. I am skeptical of it, but it's not like Tesla or Uber where the unit economics to justify their valuation are simply impossible.