Basically you're correct from a functional point of view that there's no difference in sound quality. Spending more generally gets you nicer looking and perhaps better latching connectors as well as a bit thicker cable. Sometimes the light troughput is stronger, but so long as your receiver can pick up the signal, it doesn't matter. As to whether this is worth the price differential, that's up to you.
Most optical cable you buy uses plastic fibers and that works well in relatively short distances. Glass almost always costs substantially more and is generally used in professional applications when the length goes beyond 5 meters. The following
link though is one hell of a price for glass toslink if I say so myself.