There's a little cross model confusion, which may not help in your searching. The T-2580S is a Solaris S-series trailer made in late 2005 and early 2006. The 25BH is a Sole trailer, built in 2004 and early 2005. Both have the same floorplan, both designed as entry level trailers.
The Solaris S-series was a rebranding of the Sole. The Sole was introduced as an entry level, family oriented model, but it shares the same bones and same quality as every other Sunline. I don't think it sold very well because it looked cheap compared to many other brands. Instead of fancy decals, the Sole used gold painted metal to accent with decals, which looked like a lot of FEMA trailers and base model trailers at the time. In the mid 2000s, big elaborate vinyl decals were all the rage. Now, the Sole color scheme would fit in a lot better with new trailers having gold/tan fiberglass sides. So, the Solaris S-series took the Sole idea and just painted a different picture- it has the same white siding and the same decals as a regular Solaris trailer. There were never any regular Solaris equivalent floorplans to these.
I believe the main cost savings with a Sole and S-series is in the features- it has less custom cabinets, less/smaller windows, less/smaller storage doors outside, no tank monitors, no utility porch lights on the other sides of the trailer, smaller propane bottles, probably less interior lights, thinner/cheaper interior cushions, etc. The cabinets and framework were built with the same materials, on the same line, by the same people, as a Solaris trailer, so the quality should be very similar. That said, the Sole/S-series floorplans are pretty unique and have some cool features that make them worth looking at, like the rear bike storage and the pass through TV door on the T-2380S. But, they didn't sell a lot and aren't too common.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR