Cheapest is a 6" piece of copper tubing. Doesn't do much, but it is cheap.

And the "best" one is worthless if it does not treat the SPECIFIC PROBLEM that you have.

You need to get the water tested to find out what kind of iron compound that you have.

First you need a water test for at least iron , hardness and pH.

Good and cheap usually don't go together but, you can pay way too much for low quality equipment. There is no "softener" that doesn't use salt.

You should look at a softener or filter using the Clack WS-1 control valve. If you want to be a DIYer, buy it online.

Gary

Quality Water Associates

Here all this time I thought one only has to attach a magnet to the piping EVEN plastic to remove iron Go figure