I actually thought the same thing Malte.
Before I share my thoughts on this episode, I don't know how to blacken the spoilers so if you don't want to know what happens, then don't go any further. Also, if someone could show me what they did to blacken the spoilers then I'll be sure to do so.
I thought this was a pretty good episode. Like Malte, I was expecting Sassy to end up taking over the boutique. I was also expecting her to end up becoming the antagonist of the episode after she tries to show up Rarity a couple times in the beginning of the episode. I thought she would end up becoming this season's Suri Polomare (Probably spelled her first name wrong) and try to claim the boutique as hers.
I completely understood where Rarity was coming from in how Rarity didn't want to create if it meant making your creations part of an assembly line. And while the princess dress was nicely designed, I did like the other ones better.
Also, was I the only one who noticed that Cadence didn't get a dress made in her honor? What, Twilight, Celestia, and Luna get dresses but not Cadence? The heck, Rarity?