Can using dead drops be that efficient if you are retailing on a national level? One of the convenience aspects of darknet markets is surely using the mail service as the courier. Perhaps this is for specific use cases where the sales are on a wholesale level and the economics work out on that basis.
Never thought about a dead drop that can only be located with a Bluetooth beacon only when the right WiFi network is visible on the buyer's phone. That's... A pretty good idea.