shop lift liability?

Im going thru something similar now with insurance. They are telling me that I need to have insurance above property owners normal if I put anyones car but my own in the air. I currently sell and install tires part time in the evening. To cover the building and the liability for shop with lift is going to cost my around $900 a year. Really dont have much choice on whether I do the insurance or not because this brings in much more in profit but it pisses me off they always find a way to dig into our pockets. My wife works for an insurance company so she has forced me to do this the last 4 years. I always hear the story that if something should happen without the insurance someone could sue! I threaten every year to not get it and she says then sell the lifts and tire machines! I cant win! So yes I can believe a lift would be a liability.
Rod