I paid $65 on Amazon for the s4i's. I've tried many more expensive in-ear headphones and these Klipsch sound equally as good. Two channels per ear, with nice separation - clean, not tinny treble, and moderate, tight bass (when seated in ears properly). The sound has a fair amount of spaciousness especially with lossless music.
These in-ears are quite comfortable (3 sizes earpieces supplied), even the cord with mic is a tangle-free type (even though it doesn't look like it, it has a quality feel). My only gripe after nine months of constant use (stair climber, walking, running, riding the train, yard work) is the rubber connecter - holding each cord to each headphone has split on both earphones, though not that noticeable, it is a detraction from the quality of the rest. Why aren't these rubber connectors a solid piece construction?
Just a side note: I tried the cheaper S3's for sound comparison, and they are exactly that... cheap (sound like the headphones supplied by airlines) and I mean awful.
I have not tried the S10's (pretty, but more expensive), but have read reviews that they are similar sounding to the S4's.
I always clean the cord and earpieces with iso. alcohol and use plastic, bristle type toothpicks to clean (push through) the latex earpieces; even the metal case is unobtrusive, and handy.