Ball Cactus is the Bad Boy on the Block

It seems that "Ball Cactus" anything (I don't have Ridge Ball yet) simply won't sell regardless of soil, water or fertilizer types or amounts. I've put them out, properly pruned, on steroids, and way long after everything else has sold they linger on in the nursery. (yes, the aging is arrested by 'pausing' before sending to the sales floor). To the trash they go! If you can't sell it for a buck at the Dollar Store what's the point except for cross-pollination? Thank goodness that the other 14 items on the bench share the cost effectiveness of the fertilization. Is this a bug or am I missing something?

Arthurium seems to sell no matter what. It doesn't matter whether 15 or fewer plants go to the nursery - IF something goes unsold it's a ball cactus. I've tried reducing the MSRP, pruning off bit by bit down to the seed "bump" to no avail. After 15 minutes, (priced at a dollar!) (reset MSRP before trashing), it's off to the mulch pile!

Shuffling the plant's location in the nursery didn't help either - I'm stymied.