Thanks very much for the math and "showing your work"! : )Sorry this reply took so long, but here's a two part answer.
• An estimate of which bucket your $1078 fare might be can be found by:
_ deducting the single Senior discounted rail fare from $1078 to find the fare for one Adult in a Roomette
_ which is 0.9 X (Coach Fare With The > Symbol)
_ which is 0.9 X $193 = $173.70
_ so the 1 Adult fare would be about $1078 - $174 = $904
_ but the chart in Post #38 only shows the two lowest Roomette buckets of $485 and $591
_ so the three other higher buckets can be estimated by adding the difference between those two buckets of $106 to $591 three times giving the five buckets of $485, 591, 697, 803 and 909.
_ The previous estimate (two steps above) was $904 and is closest to the estimated high bucket of $909, so your $1078 fare is for a high bucket Roomette.
• The actual high bucket Roomette fare for one Adult on the SWC between ABQ and CHI can be found from Arrow which shows $904 for tomorrow which is only 0.6% from the estimate. Close enough for me.
BTW, a low bucket Roomette for the two of you would be $485 (from the chart) + 0.9 X $193> = 485 + 173.70 = $658.70
This estimation method will work for any of the trips where only the two lowest buckets are given because the upcharges for the sleepers go in an arithmetic progression (with a fairly constant difference between successive buckets). And while Coach fares go in a roughly geometric progression, the same Coach fare (the one followed by the > symbol) is part of the total fare shown in the chart so the total fares for each sleeper remain in an arithmetic progression.