A lot :(
Surrogates are costly because you would be asking a woman to take the risk and 9 months of her life to be pregnant for you.
Plus, you need to have a thorough medical evaluation and a solid legal contract. Usually you also pay a broker fee for finding the surrogate. The costs are much less if the surrogate is a relative. Cost between $40k - $150k depending on contract terms. Get great lawyer. Best.