It can vary widely depending on when you book - prices do seem to creep up.
I could swear that the last time we looked, it would have been under 1500 bucks for the two of us, one way, from DC to Portland (the other terminus of the Empire Builder) including a “family bedroom” on both legs - but when I went to book it a few days ago the price had a) crept up, and b) did not include a sleeper west of Chicago. Or maybe it did but it was just a roomette. Nope, not for a 46 hour jaunt!
I did just book our trip - long-planned gathering next May. I just got tickets one way as we’re not sure what our return plans will be (maybe a drive down the coast and a train or flight back). It wound up being about 2600 bucks, once I upgraded the western leg to a “family bedroom”. A “bedroom” (upstairs, has its own toilet) would have been 300-400 more. Depending on our rewards points situation in a couple months, I may try to use points to upgrade that part, though a family bedroom is actually fairly spacious for 2 people. The eastern leg is just in a roomette though - but for 24 hours we can deal with it .
“They” all try to claim that it’s still worthwhile because you’re getting fed and not paying for a hotel - er, yeah, that offsets some of it, but if I spend 150 a night on a hotel, and 100 a day on meals, that’s still less than the sleeping accommodations. Let’s face it: you don’t do this for the economics, you do it for the experience.
For two travelling together, I’d almost suggest getting 2 roomettes, though that’s the most expensive of all (just looked at the prices on that route for another date).
If you go in coach, it can be quite affordable: 2 people could go cross-country for 400 bucks or thereabouts. I went to Florida in coach, a couple years back. Yeah… not doing that again. When my son travelled out west 2-3 years ago, I posed the suggestion that if he wanted to save money, he could do coach for the here-to-Chicago bit then a roomette afterward, which was what he wound up doing.
We both use CPAP machines. Not sure how we’ll manage that on the train; last time we went, we just didn’t bother as it was just 1 night. Though on that Florida trip, I did see one fellow sleeping in his coach seat, all masked up.