I simply tell people, if you can snap a picture and send it to me along with the measurements, I'll get you a quote. You can have two revisions if the job is over say $8 or 900. If this goes before a group of people for votes, I'll re-quote it if there are any silly changes. If someone in your congregation can hang, adhere..... whatever this, it'll be a lot cheaper for ya. If I need to come out due to lousy instructions or wrong parameters, that will also change the bottom-line. Now, I always considered within a 10 miles radius I could come out, but if I could avoid it..... I would.
Your people have changed the boundaries way too often to even consider the cost would not change. The guy you're dealing with sounds like the treasurer of so many churches, real estate companies and car lot owners. Kick him in the balls and when he stops screeching tell him you're no longer interested. You have other people willing to pay you for your time and expertise.