Your question is a little confusing insofar as I don't know which side you're on. It is general practice in New York for the seller to pay a broker's commission on most types of real estate, including raw land. So if the property is currently listed with a broker, most likely the seller is paying that broker (and cooperating brokers) a commission. So if you're thinking of buying such a property, you should call a broker, make an inquiry, and find out whether you're going to be expected to pay a commission.
If you're thinking of selling such a property, then, again, you should call a broker and make inquiries on what the property might actually be worth in today's market and what a broker would charge for the types of services you need.
Finally, if the implication of your question is that the commission should be lower on such a large-volume piece of property, you're probably correct. But that would depend on the broker and the services you require.
And as Tammy says, if I was selling a potential $20,000,000 piece of property, I'd probably call a few good brokers to get some of their thoughts on it.
Each company offers it's own level of services and qualifications . Interview some firms and find out what you will get for your money.
I think you were stating that the property is worth approximately $20 million. How do you know? In any case, that type of investment certainly demands care and due diligence, It is worth your time to investigate a couple of companies and ask many questions.