Personally I think it already did start to "circle the drain" and the producers realized this with an attempt to inject new cast members. I don't see this lasting beyond one more season. I have a feeling we could see more newbies next season as well.
Well that's because ratings have been going down so they're been cutting costs. The originals (bidders + auctioneers) get paid to appear in the episodes and it's continued to go up. They are paying Darrell the most to appear apparently.
The dynamic has really changed from the start though. Obviously no more Dave, but Jared & Brandy didn't have much money then. Now unless manpurse shows up they have the most money to throw at units.
Darrell I don't really know what's up with him. He doesn't really seem like he cares too much anymore and just hams it up for TV time. Maybe he did really make several hundred thousand off that paintings unit and has dialed it back.
Barry's sendoff wasn't bad. The highlight being that he brought back all his sidekicks lol.