While approximate land value calculators and charts are available online for most areas of the United States, sellers should use these figures only for broad estimation purposes. Arriving at a more exact price point to use as a listing price is best done by a real estate professional with a solid track record of successfully selling the type of land being sold.
You can also look to certain companies and organizations that have a concentration of people that may fall in the above mentioned roles such as investment companies (i.e. Charles Schwab, Fidelity), financial advising companies (i.e. Morgan Stanley, Merrill Lynch). There may be a higher concentration of people who can both afford and want to build their own custom homes or to build income-producing properties. Try linking yourself to financial advisors who may already know of people who have these types of dreams. This isn't a comprehensive answer of all the possibilities but just some thoughts. Good luck!