I charge a 30% premium for my time on site. Working from a location of my choosing is more productive. When on site, I am endlessly harassed for meetings and ch

I charge a 30% premium for my time on site. Working from a location of my choosing is more productive. When on site, I am endlessly harassed for meetings and chats and people coming to say hello (and oh btw can you help me with <insert issue>), whilst it is expected that my productivity remains the same. Some clients actually expect an increase in productivity. Being on site is more work, so the client pays more.