Cost is roughly 2x (at MSRP/inflated MSRP) over a 3080, so if you can buy a 3080 there's no reason to buy a 3090 for hashing. Hashrate is something like 20-30% more than a 3080.

Drive miners to the high priced cards while leaving the price/performance market for gamers.

The extra cost over the 3080 is probably not worth the minor increase in the hash rate for mining.

3090 availability is relatively good at the moment.

Relative is a broad statement depending on where you live. In the US, Newegg has been going in-and-out of stock but mostly out.

This has very much not been my experience in the US.

I'd love to see a few links. I haven't been able to purchase them, checked Amazon, Best Buy, and newegg.

Is it? I haven't seen one in stock in a long time. People are setting up sniping programs to auto-buy them.