I think that listing is an anomaly; I see models with similar specs for cheaper (~$5000) on Lenovo's site. But they do come with Nvidia Ada GPUs.

The Lenovo ThinkPad P16 Gen 2 can have up to an Nvidia RTX 5000 Ada Generation (16GB GDDR6).

If you pay MSRP for a thinkpad you're doing it very, very wrong

Where do you get them instead? eBay?

Lenovo sells refurbished Thinkpads on eBay, yeah. I bought one at the start of the year for about 30% of MSRP and I couldn't tell it wasn't brand new

If you're intent on getting a new one they still offer regular deals on their store