If the electric grid ever went out in the U.S., one of the things you would loose is the water going into your home. A person can go without food for a few weeks but water, they would only be able to survive a couple of days. A water well can help supply your farm and family with water if the electric grid ever went out. Having a well can also significantly reduce your water bill.
Water well costs do vary depending on your location due to elevation and type of ground. For instance in Miami, FL a well could cost about $1,500 but in the Ozarks you are looking at anywhere between $6,000 and $15,000. The well needs to be at least 50 feet away from your septic tank. Remember that you will need to periodically test the well water to make sure that it is drinkable.
In a place with so much precipitation you could choose a rain catching system instead and those costs vary on the size of the system you put in place.
Here is a video discussing the pros and cons of a well water vs a rain catchment system from OGB on Youtube.