Posted By:
runscottLike Pete said, the Boston cards shouldn't be considered too special either.
My thought was that the "No B" cards slipped by the printers because it wasn't something that stood out. It would have been a different story if they had run out of the green ink, since it covered the entire background.
Could be that a bunch of the "no red ink" sheets were printed and no one even noticed - so enough cards made it to production for people to later notice the variation and tack on a premium.