Without getting into the figures, the simple answer is IF you get stung for import duty, it's likely to be quite substantial, and sometimes more than the item is actually worth (they add some quite substantial admin charges).
HOWEVER, most things bought in this way get through without import charges - they just arrive. One very common ruse is for the seller to declare the package as a gift, which doesn't attract duty. I'd expect most crafty things bought from Etsy and declared as a gift would be very unlikely to attract charges (I'm not saying that's right - just that it happens).