Hohenzollern is a puppet of Prussia, and because of that it is in the same custom union. However, it often happens that no land route connects Hohenzollern with Prussia, generally because the surrounding countries leave the CU or are annexed by another country not inside Prussia's CU. With 0% market access, Hohenzollern can only consume what it produces; setting a trade route would import goods into the Prussian market, not the de facto independent Hohenzollern market. However, with only a few thousands pops in the workforce, there is no way for it to produce enough goods to fulfill needs through subsistence farming, which raises prices and makes everyone poorer. Meanwhile, any building instantly overproduces goods, driving prices into the ground and destroying profitability, meaning owners, for example aristocrats, lose all their income.