"It breaks my concentration. That makes things take more time. That makes things cost you more money."

edit: Suggest that he ask you if you're busy over skype. Talking face to face is more effective, and I'd hate to try to discuss something over it, but interrupting flow really sucks.

Because bosses and managers are suppose to support their direct reports by obtaining a work environment and tools that best enable them to be productive... if he refuses to contact you via skype, when he asks you a question verbally, respond by typing a skype message. It's not okay for managers to treat others how they (the manager) wishes or wants to be treated... great managers treat employees the way the employees wish to be treated (as long as that treatment is ethical and productive).