If Amtrak wanted modern lie-flat seating I agree that it could be done, but it would require a massive up-front cost that would come with several revenue focused trade-offs. Due to what I perceive as the inherent limitations of installing modern aircraft focused hardware on much older trains I'd expect long haul lounging pods to be offered at or near roomette level pricing. I'd also expect this type of refurbishment to be accompanied by a much denser coach layout that makes room for more seats and levies surcharges for previously included features like free checked luggage and a relaxed carry-on policy, as well as offering a litany of premium option upgrades that allow coach travelers to buy back what was lost in the process (pitch, width, luggage) and then some (priority boarding and seat location preference). It's the idea that long haul lie-flat seating can be sold at regional upright seat pricing that confuses me.
Ok, I'll bite. There is a thing called market segmentation that all businesses do. Airline business class with lie flat seats are a different market segment than the people that would want them or a section.
Business travel tends to be less flexible than leisure travel which airlines understand and price accordingly. Also, since businesses tend to be paying for most of the lie flat seats with less flexibility, the prices are higher largely because they can be. They know a company will pay for it so they will charge it. For example, let's say a flight from two points with a lie flat seat costs $1800. I the average person couldn't afford that, but any decently sized company probably could and can write it off as a cost of doing business. Paying for nice things also helps with employee retention, so it's cheaper to pay for some nice flights than to higher a new person.
I know you'll say something about random people who think of themselves as too good for coach buying a business class ticket, they exist, but they aren't the target demographic for most airlines selling business class. They'll happily take the money and market share but that doesn't take away from who the product was originally designed and priced for. And they'll also upgrade people for free and for cheap. One rule of business Amtrak doesn't seem to care about is it's easier to retain a customer than to get a new one. So running a few freebies per flight keep people coming back and a cheap upgrade is better than making $0, or the exact opposite of Amtrak's attitude.
Even if Amtrak reduced the pitch of its seats to 33 inches from 39 for regional coach, it's only going to get 6 or so extra rows of seats per California Car and even less for a Amfleet car. And if they did it on long distance trains, they'd tank their own ridership numbers. And even if you could fill the extra seats on short distance trains, 12 extra people paying the same amount for a ticket isn't going to justify the cost even if you leave one "regular" coach and charge more for it.
Paying for baggage is about the only thing they could do to squeeze passengers for more money and I'm personally surprised they haven't done it yet.
As for the pricing, setting a price is more complicated than cost/space. Even on airlines, business class passengers generate more revenue per square foot than coach passengers do. So it's not out of the question for Amtrak to set the price of a Delta One/Section much lower than a roomette, but still covering it's cost (or at least setting the fare buckets to do that over a year) and raising revenue off of existing sleeper tickets because they'd mostly be attracting richer tourists if the more price sensitive "I'm riding this for transportation" types aren't buying as many sleeper spaces. And on top of that, still making more per square foot than a coach seat.
Amtrak doesn't have a market segment like business travelers on airlines. Which means Amtrak riders are much more price sensitive. Which means they're not going to be able to strip someone of food and privacy and still charge them the same as if they had food and privacy.
As for the cost, I never said it would be easy or cheap, just that it's doable. And doable with exceedingly conservative numbers. Also, Amtrak did put roomette modules into Amfleet cars at one point, so its not out of the question for them to do it.
let alone a trip that takes two or three days 
