You're right. I was too quick and jumped the gun by calling it "bad analysis". However, I do believe that the source of this offer is the larger factor than the dollar amount in OpenAI's valuation of the offer. If this was anyone else offering to buyout OpenAI then the argument makes sense, but Sam Altman and Elon Musk seem to hate each other's guts and are even resorting to name-calling online in the fallout of this offer.
https://xcancel.com/elonmusk/status/1889062013109703009
There's a good chance there's more to it than I realize, though.