With the latest update (Welcome amiibo), the ability to sell your town for bells was introduced. However, I am fearful of accidentally deleting my town. How do I find my town's value?
From the main screen you can talk to Isabelle and select the recreate town option. If your town is worth enough, Tom Nook will appraise the value of your town. Be warned though, your fear of accidentally deleting the town is valid because if your town is not worth enough Tom may delete your town.
Therefore, it is not worth checking the value of your town unless you plan on restarting anyway. Seeing the value beforehand just allows those wanting to restart to plan further and delay selling until it is at a value they prefer.
See this Reddit post for more information.