The $600 is for 15 USB only. Buy in bulk to save $ . Wireless USB bridge dongle IoT control module for connectivity to smart devices for monitoring, control, remote viewing of activity, employees, kids, home smart devices, solar panels, video cameras, phones, tv, laptop, desktop, refrigerator, oven, lighting, swimming pool heater, hot tub control temp, ac/heat, stereo system, intercom, gps systems, voice control systems like Alexa, check in on your pets and kids while away, you name it. If it is internet capable you can most likely connect to it. Software required for some controls and may be an added cost. These come with software that is updated remotely, periodically, by the devs. 30 are in stock now. Only selling two bulk sets of 15 and price is firm. U.S. only. Shipping cost does not change by volume. Thank you:).