Let's start with big box brands like GE, Whirlpool, Kenmore etc. They are indeed less expensive and possibly more prone to mechanical failure and perhaps you will not get as many years out of them as you would with a Fleck or Clack valve head. However they are less expensive and most will give you at least 5 to 8 years of service without problems and I have seen some that are still working after 15 to 20 years. Neither Fleck or Clack sell tanks, media etc. When you buy a "system" someone assembles the valve, tanks, media etc and packages it as a unit. Both Fleck and Clack valves are used on a variety of set up's that have been re-branded under another name. Yes, Culligan, Kinetico etc are more expensive no doubt. You have to sign up for service contracts with them also and since they are proprietary valves and equipment they are very difficult to get parts for. If you or your mother is handy you can get Fleck online through several dealers but not Clack because Clack decided they were tired of dealing with unscrupulous internet dealers and hacks. Your local plumber should be able to steer you in the right direction though.