Okay, I am going to do the basic evaluation based on adult fares, not senior, since that is what is easily referenced on
@niemi24s' chart.
Just now, I ran it on Amtrak.com for 4/15/25:
1 Bedroom for 2 adults at $2506. $2506 - $290 = $2216, 6th Bucket
2 Bedrooms for 4 adults at $5626. $5626/2 = $2813. $2813-290 (adult rail fare) = $2523, 7th bucket
3 Bedrooms for 6 adults at $8,439. $8439/3 = $2813. $2813 - $290 (adult rail fare) = $2523, 7th bucket
4 Bedrooms for 8 adults at $12,676. $12,676/4 = $3169. $3169 - $290 = $2879, 8th bucket, the top.
You discovered a bucket jump. Actually, two of them. These results show that there is currently one open bedroom allocated to the 6th bucket, after that it jumped to the next bucket, with 2 Bedrooms in the 7th bucket, then jumped again to the 8th bucket. If you exceed the lowest bucket inventory on a single reservation request and there is inventory in a higher bucket, the price for
all the rooms requested jumps to highest price for any of them. If there is not inventory in a higher bucket, it will return "Sold Out".
Further, up to 5 rooms can booked for 8 people, but it will not go any higher than 5. There is not enough inventory to accommodate 8 adults each in their own Bedroom, so the total open Bedroom inventory is 5. The cost for 8 adults in 5 rooms is $15,265. It also means 3 doubles and 2 singles. That means a rail fare adjustment of $290 each for the 3 rooms with double occupancy to get single adult room pricing to reference back to the chart. 15265-(3x290) = 14395 adjusted total for single adult occupancy of 5 bedrooms. 14395/5 = 2879, again, high bucket.
Conclusions:
1. Bedroom total available inventory is 5. Those 5 are allocated with 1 in the 6th bucket (2216), 2 in the 7th bucket (2523) and 2 in the 8th bucket (2879)
2. If there were two sleepers currently assigned to the 4/15/25 departure, the total inventory would be 10. One sleeper, 5. Since it is very early, and there are 5 open bedrooms, it is highly likely only one sleeper is currently assigned to the 4/15/25 departure of train 3. The chances of all five bedrooms in one whole sleeper being sold out this early is unlikely. If there were two sleepers, I would expect to be able to book 6, 7 or 8 adults into singles. My opinion therefore is that 31 car is not slated to run next April on the SWC as of now. That very well may change.
3. Yield management has actively been fooling around with those departures for the SWC recently. The allocations and prices have been jumping around since this discussion started. My guess is they'll settle for awhile now, but yield management on the SWC/TE is confounding me and is unlike the patterns I have come to expect on some other trains I investigate more frequently, like the Builder. However, all inventory now seems consistent with a fairly common pattern of one room in the lowest
open bucket, then more in higher ones, all of them high-ish.
I've always been able to get multiple bedrooms on that date through this whole discussion. I ran several other dates in April 2025 and get similar results, with the allocation of the first 3 rooms varying between 1 in the 6th bucket and 2 in the 7th bucket and 2 in the 6th bucket and 1 in the 7th bucket. That is also the inventory allocation for the last date open for sale right now, 5/16/25. It really looks like one sleeper assigned, no sales yet, and they've consistently allocated the April departures in a similar fashion. Finally, railsforless.us is giving different, and lower priced, results than Amtrak.com right now for these dates. Perhaps they cached old data?
With only one room in the 6th bucket now for your date, and no date at all lower than the 5th bucket for Bedrooms on the SW Chief between now and then, you may want to think about grabbing that 6th bucket price, which works out to $2448 for two seniors (2216 - 29 senior discount one rail fare + 261 senior rail fare). Prices may drop to the 5th bucket, but also when they actually start selling, that 6th bucket room will be the first to go. I normally wouldn't buy this far in advance and would wait for things to develop, but with only one room and the steps up after that of over $300, then nearly $700, I'd grab it. Keep monitoring though, and ask for a partial refund if it drops.