As in most things, it's the smaller price points that are going to be the "bread and butter" of the business, and it can lead to larger sets being purchased. Plus small sets fit better into the average adult lifestyle. We can all make space for collectible historical figures. It's much harder to make space for (and justify) a whole castle. So, I don't expect buildings to become top selling items.
Like the male fairies. I want them, but they come in larger sets, and I don't have the space/desire/money to collect fairies as a theme. I just want a couple male fairies to hang out with my existing fairies. I don't want a bunch of pink and purple accessories.
But, again it would be helpful if people other than established collectors *knew* about these DS sets. Even if I google something super specific like "medieval tailor shop toy", the Playmobil website doesn't come up. The Amazon and Ebay listings do. Playmobil comes up when I google "medieval tailor shop" but not when I add "toy." That's absurd. Their website is basically reaching only people who already know about Playmobil.
(Dear Playmobil, please let me fix your SEO. You need set descriptions and metadata.)