I just got the reusable thunder and I already had the blaster from a while ago, so I just noticed this as well. Both are 135 hardcore. I can also note that the dragon sword is 135 know-how, so that's why it seems like either the blaster or the thunder should have been charm.

This gets into more just questioning the overall balance of the items in general, but I'm also thrown off by another gold item for that same slot, the psychic scepter. The green items katana, magical wand, and mini treasure are all 30-35 of a main stat and 1.8-1.9 crit. Then we've got the psychic scepter with 2 crit and nothing else, which is just flat out a worse option than any of the "lower quality" items I just mentioned (the only green item it's better than is the one just simply called sword which only gives 1.2 crit and nothing else). I'm also aware of one green item for that slot, the tube radio, with 50 hardcore. But I haven't seen anything for 50 charm or 50 know-how. (I don't know if that's just weird luck or if those items really don't exist.)