It depends a lot on the country! The whole system costs here a lot but it can be done in stages. The septic system is around 800$, the percolators another 600$, the drill is 400$ and the rest of the filters are another 200$, a pump is 100$ and the water softener is 800$ with the small filter for drinking water another 150$.
That 800 feet well will be costly but in time it will pay for itself. I didn't say it was the cheapest house, it was the cheapest energy-efficient and off the grid :D
a septic system here will run you $10,000-20,000