1 Drilling the well hole, installing the casing (a tubular lining that prevents the well hole from collapsing) and adding a well cap (a tight-fitting, vermin-proof top seal) typically costs $15-$30 per foot, or $1,500-$3,000 for a 100' deep well, and $6,000-$12,000 for a 400' well.he most common method of well construction in the United States today is drilling, which requires a fairly complicated and expensive drill rig, usually mounted on a large truck. Drilled wells are typically 100'-400' deep but can be 1,000' or more.