I would say they are not that rare. For instance, you can still buy each of those variants on KBtoys.com for $8.99 any time you like:
http://www.kbtoys.com/genProduct.html/P ... stock/Y/D/And it's been that way for weeks, can you imagine if an online store had Dark Phoenix or Stealth Iron Man and they stayed in stock that long? I can't. That's why I have all the LCBH variants and practically NO ML variants.