What is the market value of vacant lot per square footage in Highland Park California?

My neighbor is selling part of his lot to me but neither him nor I know the market value per square footage on lots in the zip code 90042. He has checked with the city and he was told it was possible to sell a portion of his lot. We just need to know the market value per square footage to close the deal and have the city do it's part. Can you tell me or can any regular real estate office tell us?