No, it isn't a customs charge per say but it IS still out of SM/CP's control.  I know because I used to make and ship jewelry to other countires and I WOULD call UPS to verify each and every charge that would be added to I could tell my customers exactly what it would cost. 

GUESS WHAT?  UPS added on an additional "processing fee" that they didn't even disclose to me!  That is why I no longer ship anything anywhere.