How much are you willing to pay? There are (a very few) luxury train trips in Europe. Maybe $5-10K NY-SF or NY-SEA would cover it in the US? It's totally doable if there were a market; basically upscale the long-haul Amtrak routes with higher-end accommodations and food. The evidence suggests there's not the demand.
I think it's partially a chicken-or-the-egg problem. Honestly, I didn't even know these private rail cars existed until this article. I feel like if the Kardashians took a cross-country tour in one of these things and Instagrammed it that it would be all the rage.
You need a critical mass of volume though. You can get pretty nice suites on Amtrak today on the long-haul routes. It's admittedly not luxury in the sense of really first-class food and everyone dressing up but probably a nice slow travel experience so long as you don't care too much about arriving as scheduled. I'm not convinced there's that big a market for don't care about cost + don't care about time.
Sleeping cars, while still existing, are pretty much a dying species in Europe.
Significantly higher speeds made them pretty much obsolete.
While, for example, it used to take 7+ hours to get from Zurich to Paris (and artificially longer, if it was a night train) the trip now takes 4 hours by TGV.
I've actually contacted for a quote before. I've thought about doing it for a birthday ;)
I was quoted 7500 per day minimum. Plus staff, food, etc.
My trip would be Den -> San Fran the problem is the most realistic response from a charter company I got was based in Chicago! So you have to think about days to get to your location, plus the return. Plus your trip.
I've also really wanted to do a Belmond long trip but they book sooo far in advance and I usually dont book trips until a month or two out. Maybe I'll treat myself for a 2021 ticket for my 30th birthday lol