Just some philosophical banter: Who decides what the prices should be? From what I see base materials, juices, PV's, cartos, etc., aren't very expensive. Mark-up isn't regulated. It's a free market. So it's basically up to the retailer to decide how high or low his profits will be.
And then, how original was your s&m concept in the first place? One could argue that it wasn't copied... but just re-hashed. Just like every hit song... there's only so many chords available. Ergo, there's only so many ways to sell this stuff. But, I know you offer things and other benefits that the others don't. So, you will definitely always have a loyal customer base (mine included). But, from a consumer standpoint... it's really nice to have options.
Delivery time is also an issue (especially when you're running out of stuff quickly).