This valuation is a function of early accumulation of compute. They could rent it to Anthropic, or poach more Anthropic engineers.
Not sure how long you'll be able to sell compute to anthropic for. They are constrained right now but they have an insane pipeline of take or pay contracts, and if those are delivered they'll be drowning in compute in a couple of years time.
Anthropic has a higher valuation than OpenAI.