"European" cylinders are oriented opposite to "North American" cylinders (i.e., when installed, the pins are on the bottom of the keyway) -- so, as a result, folks who are regularly working with those cylinder would want a pick gun with a downward action. (That's explains why they bother to make pickguns in both styles.)
Sadly, the price difference is like anything else... there's probably very little cost difference in the parts, but anything "different" always carries a higher price (either because of legitimate reasons related to supply-and-demand, or just simply because they can charge more).
Hope that helps!
