My manufacturer offers the service to me for an added fee. If I sprung for it, I would probably have to slightly raise my prices. I spend the money on branding the eCigarettes that I sell, because those are what you and everyone else are going to be looking at. It is also a key indicator that the product came from my business in the event of a RMA (failed unit). Let's face it, once you take your shiny (or matte ;p) eCigarette out of the box.. do you ever really look at the box again? My guess would be rarely, if ever.. I'd rather keep my prices fair and competitive.
If you want more info, I have no problem sharing it with you. Just shoot me a PM, or an email.