Liability insurance

I have a wooden v quad style billboard each face is 8x16. It’s on my land and I’m hoping to build more in the county I’m in Pennsylvania but looking into insurance my regular agent wants literally all of my gross revenue for insurance. I also called another company that do some insurance in this business and they still want half of my gross revenue in insurance I don’t understand how u make money when they take half he is saying 750 per face per yr it only cost 6k to build them there in a very rural area Hopefully someone can get me lined up with a better agent for billboards