Not that I know the history of that exact piece but with Steve mostly focusing on pre production and the label on that MOC reading "EP B-Pilot" it is very likely part of the pre production realm and not an error/unintentional miscard.
EP stands for Engineering Pilot, which could mean a sample, a bubble test, test packaging etc (Chris's white 3 pack box is an Engineering Pilot for example)
Another thing is, the ERG figure was released on the earlier 65 back and the B-Wing debut was the 77 back, this is a common theme with test packaging/pre production pieces, new figures are mounted on older cards.
As such, cost wise it is probably a $500+ piece if it has solid provenance (which it most likely does if Steve owns it!) I know I would easily pay that for a well documented sample/EP