This is weird. I remember when using my original 60 card-rainbow for FG killing, I wanted to switch to CCYB. I had to sell a few cards though and sold some sundials at the time. (only got one upped sundial left now, so I know I sold 'em at some point)
Either I was very retarded at the time and didn't check the sell price (and got screwed), or this is a new bug. It's probably both.