I'd also much prefer to know in advance exactly what I have to pay for something, especially if it is supposed to be a "standard" product.
But that industry looks very competitive and I guess that hobbyist quantities of special boards is not where they make their big money. Also, "upselling" is a phenomenon which known here as well, In such a way, incidentally, which make the Chinese attempts at it look quite tame.
Anyway, it is good that the risks are mentioned in this thread, identifying where hidden charges could appear.
I have to play a bit of a balancing game when ordering. The transport cost is high relative to the product cost so I have to batch my orders. However, over a certain limit here (about $70 including shipping) import duties and, worse, the one-off administration costs of collecting those import duties, kick in heavily, This delicate balance can be messed up if additional charges appear for the product. If the order would be huge, which for me it never is, the cost per board (delivered) would, once a gain, be cheap.