There are combo packs for the following monsters (presumably you can buy one, rather than both):
Bella Baal / Little Red Furry Cap
Fightreer / Avaritia
Obsidiane / Yndra / Sylvannis
Plus there are sales where you choose the rank of the monster (normal, 1 star, or 2 stars):
I don't know about you, but I am very happy with these offers that will be around in early July (maybe earlier). I will buy 4 of the bottom 5 regardless of price, and I will also buy Bella Baal if she can be purchased individually.