Probably not a good time to tell you how much a very large lot of UK packages cost me last year, then (although there was a Mountain Boy package among them). Those were UK release, though, and only one playset box, the Sprinkles version Waterfall...I think the price went up more because of the pony boxes than that one, as it's generally more common than the Cascade version.
Is it $20 for the box on its own or factoring in shipping? That's always a factor for me, because unless you want them to flat pack the box, the size of the parcel can play a part in cost.
I am a bit biased from UK availability, where Grooming Parlour and Show Stable boxes are quite common, but $20 seems quite a lot to me for a Pretty Parlor box. Even more so for the tub...Not knowing what others you need, it's hard to comment. Maybe Hathorcat would have some ideas about pc?