I'm pretty sure this Dell would have used this Sony panel:
https://pro.sony.com/bbsc/ssr/cat-hdr/cat-hdr1/product-BVMX300/
That's a $20,000 pro monitor. The cost of course would be driven down by significant volume increase with the Dell.
I think Dell could pull a profit at $5,000. It would absolutely destroy every other monitor out there and people like me would pay for that. The real problem was Thunderbolt only for 4K 120 Hz. They could have shelved the monitor until DP 1.3/1.4 TCons come available sometime this millennia.