The real numbers were last reported in the bar graph on page 11 of this presentation:
https://www.amtrak.com/ccurl/778/373/Amtrak-Covers-88-Percent-of-Operating-Costs-ATK-13-022.pdf
... the Empire Builder is actually the best of the trains west of the Mississippi. The Eastern trains do better, unsurprising because they have shorter routes with more and bigger cities.
The Eastern trains enjoy more benefit from sharing parts of their routes with overlapping corridor trains or other service. The state-supported corridor trains pick up most of the station cost -- tho that is not any make-or-break figure -- and probably have better upkeep of those track segments. So, the
Lake Shore Ltd. shares costs with the
Capitol Ltd CHI-TOL-CLE, then it shares costs with the
Empire Services BUF-ALB-NYC.
The
Silvers, Palmetto, Crescent, Carolinian, as well as the Amtrak Virginia trains to Norfolk, Newport News, Richmond, and Lynchburg enjoy having station and other costs split into dozens of small shares north of D.C. and down to Richmond.
Adding the
Lynchburger shaved costs from the
Crescent and the
Cardinal, and a train to Roanoke will help there too.
But again, station costs aren't that much. The
Zephyr isn't losing big bucks because it has too many stops in Utah and Nevada deserts, LOL.
The largest benefit may be the hardest to quantify: Obviously, the main benefit from state-supported corridors is the
frequency of service. Customers are happier when they can chose to leave early or mid-day or later. And potential customers see passenger train running alongside the roads more often, creating a "
saturation marketing" effect like you get from seeing McDonald's golden arches every few miles along the road. Each burger stand -- or each passing train -- "advertises" for the others. In those ways, and many others, the corridor trains strengthen
the Amtrak brand, and give Amtrak a larger share of the potential customers' "mind space", in the jargon of the advertising and marketing types.
Sadly, the Western trains rarely get any benefits from sharing service on corridors. The
Coast Starlight gets help from the
Cascades and the
Surfliners north of L.A. The
Empire Builder also gets some glow from the
Cascades service. But more healthy corridors -- like CHI-St Paul, CHI-Omaha-DEN, and L.A.-Maricopa (Phoenix)-Tucson, for example -- would greatly help Amtrak and all its LD trains.
Further to the general rule that the cure for what ails Amtrak is
more Amtrak.