Calcium reactors are pretty simple devices. If you know how to work on them, they are a godsend! $50 is a steal for any calcium reactor, but that is not where the cost will most likely end. Does it come with a CO2 bottle and regulator? Is there an insert to add a pH probe? If you want it to be "set it and forget it" you will need a controller and electronic solenoid. There are many dangers to calcium reactors if you don't know how to use them properly, or if it is oversized for the aquarium. And then there is the second chamber that spazdad mentioned, which you can buy separately, that raises the pH of the effluent water so it doesn't drop the pH of your tank. I say buy it and study up on them. That way when you are ready to take that leap it's already there.