What's the point of discarding helpers, as it is said in the rules? Is there a limited number of helpers available for the player? If I get it right, the helper you may keep the helper as long as you want before playing it.
There must be something I missed.
The cost of a 2-pack is dictated by the larger of the number of shops or the number of helpers you currently have. So if you have a large number of helpers, you may want to discard some to lower the price of a 2-pack.