When it comes to stainless steel used in demitasse spoons, 18/0 versus 18/10 isn't a statement about the "quality" of the spoons. Both steels can be used to make the same high-quality silverware, but the 18/10 utensils will cost more because of the raw cost of the steel. And 18/10 stainless steel will give your silverware a more silvery appearance - good for ornate patterns of demitasse spoons; less important for simpler patterns of spoons and other tableware.
And when it comes to the appearance of your silverware (and this also affects its cost), the specific care taken during the final steps of manufacturing is one of the top determinations of why some patterns look nicer and cost more. It always costs more for a manufacturer to do more careful processing of a manufactured item. But there are several things that are critical in the manufacture of demitasse spoons.
First, look carefully at the edges on your silverware. If there are squared edges, you should be able to tell something about how the manufacturing was done. Squared edges on a utensil are usually (and simply) stamped out quickly by a machine using very high pressure. For lower cost silverware, these edges are then quick-polished as simply as possible, just to remove burrs and anything that is actually sharp. In higher quality silverware, the edges are smoothed more gracefully so that they will not be sharp.
And second, look at the roundness and flow of any of the ornate patterns on your demitasse spoons. Higher quality silverware will feature crisper articulations of any patterns (leaves, lines, etc.). And the spoon – viewed as a tool - will have a more rounded look to it.
If you're buying stainless steel demitasse spoons, and you want to maintain their lovely appearance, you should pick up some stainless steel cleaner at a hardware store. Even the very best stainless steel silverware may get (very occasional) corrosion and discoloration. A little cleaner every so often will make your spoons look brand new.
So ciao for now, and salute' - you deserve the best when it comes to a set of spoons to match your excellent espresso.