Get an analysis. Most labs nowadays have test that include dollar value of nutrients in compost and manure by the ton based on current, local fertilizer prices. I have a 185 bushel spreader that usually holds anywhere from 6 to 10 tons of dry matter based on the density of material I am spreading. My last product I spread was composted horse manure, I spread about 8.5 tons per acre as is, was .69 dry matter. Each ton as is came back at around $20 per ton crop nutrient value, as is. So you would need to find out how many tons he hauls at a time, and get a dollar value test. If he spreads it then it may be worth it, if you have to spread it, then it may be too expensive. In my case I did a lot of spreading, If I had to pay for it then I would have bought fertilizer.