But I also can guess that just about everyone in coach would love to sleep horizontally.
I agree with this. I don't think it's a matter of Amtrak needing to offer a more reasonable class of sleeper. Sure, there may be a demand for that, but there will always be a demand for coach too. So, as long as there are coach cars, there will be people wanting to get out of coach & sleep somewhere else.
Here's are two extremely easy solutions, both of which will increase Amtrak revenue:
1) Charge for lounge access. Possibly give sleeper pax free access, but make it available as an upgrade for coach pax. Then, if coach pax have paid for their upgrade and feel like sleeping there, more power to 'em.
2) Sell lounge car seats as a fare. I know they're uncomfortable long term, but perhaps if Amtrak sold them, they could use some of the revenue to refurbish them a bit.
Long term, I don't see how Amtrak justifies this free lounge space. As airlines do, they're going to have to monetize everything.
Secondly, I still think that the reason sleepers cost more is because of demand, not because they're inherently so much "better" than coach. A superliner coach can seat 62 people upstairs. Theoretically, you could fit 20 roomettes with 40 people in that space. So, if Amtrak was literally charging for the amount of space it sold, a roomette should only cost 50% more than a coach seat.
Of course, that doesn't happen, because supply & demand drive the price up, just as they do with Business Class and First Class on an airplane. So, even if some kind of slumbercoach did exist, and there was a demand for it, that same demand would drive the price above what many people in coach could pay, thus leading them to sleep on the floor of the SSL again.
And to me, the floor sleeping is the real issue. I tried to traverse the SSL one night & nearly tripped over sleeping people many times. That can't possibly be safe, either for the passengers or the crew trying to walk through - especially in the dark at night. They can let people sleep on the seats, but they shouldn't allow safety violations.