Not sure if it's intentional, but I haven't been able to find a single instance of Ghost Outfit 1-5 ingame or on the forums. I've seen plenty of 6-10 on sale and worn by other people, and I personally opened 40+ boxes and have multiples of 6-10.

Hey karcaroth,

 

this seems intentional. It is very likely (actually I'm 100% sure) that the other ghost costumes (1-5) will be available during the event instead. (bot not 6-10)

so that you can achieve half of them in mystery boxes and the other half during doing some event stuff.

I hope this cleared things up a bit.

 

BR

Gami