The kinetic energy of the mass of exhaust gas carries it along the exhaust pipe, and causes a pressure build up ahead of the mass of gas and a partial vacuum behind it. This principle is used in a tuned exhaust system.
Culligan - $2352 ($2053 w/o R/O unit) Culligan Gold Series (10), Good Water Machine. If I were to look at price only, I would go with either the cheaper Ecowater system w/R/O at $2698 or the Culligan system. At almost $4k, the Kinetico system seems greatly over priced.
Culligan offers rentals, monthly payment plans and even rent to purchase agreements. No matter what your financial situation you will probably find a solution that works for you. Overall, you can expect to spend between $2,000 and $3,000 on a moderately priced unit. Of course, the in-home rep is going to try to upsell you to the more expensive units or the all-inclusive maintenance and salt delivery options too.