you know, i spent quite a few of my early working years in bakeries, and pastry shops.. and there have been many times that i've thought it would be great to do this to customers that were a crazy pain in the ass, or even those that demanded a cake that was going to look awful, but were convinced it wouldn't look awful, then complained about it looking awful, etc... there are a lot of straight-up enraging things that tend to happen when you're dealing with people that want a cake.
that being said, WOW. there has got to be part of this story we're not hearing here, because man, i know 30 bucks isn't much but just make a simple cake, or a tiny cake, or something, this person NUKED that bridge on the first volley.
there's got to be something, though. the person owed the cake maker 20 bucks from before, so it's not as if they hadn't done business together before. if this is just a random snap though, watch out for those cakes... because there's a bomb coming at some point o.0