I'm not into trains at all, but the American Association of Private Railroad Car Owners has some pretty nice looking cars you can charter:

I guess it starts at $30,000? Though that might be for an entire train, not just the cars above.

That seems to be chartering the cars from Amtrak, though, not from the private car owners.

I clicked a random one and it was owned by a local club not amtrak

	▲	bombcar 6 days ago \| parent [-]
		Almost all of them are owned by clubs; even if you were Buffet and wanted to own one it’s cheaper to do so via a non-profit club.