To be fair on the cake:

Most regular cakes are small affairs. If you go to that same baker and ask for a 3-tier, ornately decorated cake that will feed at least 50-100 people and has a keepsake decoration on top, it'll be more.

Cakes like that are a different beast. They require special recipes so they don't collapse themselves. I know professional bakeries are able to spend less time than I did making my sister's wedding cake - a 3-tier affair - but they are still a decent amount of work and effort. Doubly so if you are paying the baker to transport and assemble the cake.

So yeah, of course wedding cakes are expensive, depending on the bells and whistles. But so are equally decadent cakes with the bells and whistles.