If you were to do a little research you could find out some of these facts for yourself. But, since you seem unwilling or unable to do it for yourself, I will do it for you.
The Stenner pump I quoted includes the pickup and the injector and necessary tubing and a replacement pump tube. I previously provided you with the link to the solution tank. As I previously posted the cost of the pump including delivery (with accessories) is $205. The solution tank is $35 delivered.
As to your assertion that it is the "cheapest type pump" I will observe that Stenner is a quality brand and, in my view, is not appropriatly referred to as the "cheapest type pump."
As to a retention tank--it doesn't seem to me that it is relevant-because it is required whatever cholorine source is used. But, since you keep bringing it up I will provide the information. An 80 gallon retention tank, or the tank that you include in the system you quoted in an earlier post, is availble for approximately $450 delivered. So the delivered price for the solution pump (with accessaries), solution tank, and retention tank, plus a large supply of chlorine from the local supermarket is approximately (205 + 35 + 15 + 450) $705. This is LESS than the price you quoted ($773) for the erosion pellet feeder, chlorine pellets, and retention tank.
So, I believe I have fully supported my statement that "An injection system for chlorine is lower cost--both to buy and particularly to operate--than a pellet erosion system. ".