u/73Cancerous

We have a little lot of land for sale that we want to sell, but I'm unsure of what we can charge for this lot. There is someone who has expressed interest, and that will, in essence, double the size of their land. Size is only .09 acres, but like I said, it will double the size of their entire property. I don't want to be an extortionist, but I want the best value for what they are getting. Any thoughts?