You're missing what you discover when you do do the maths. For example the kit contains only 20 of the 44p ones, the other 80 are about half that.
It's not a huge premium, e.g. at QVS the kit is £51.54, and the contents cost £47.70. I guess if you need the organiser case it's not a bad deal.
I don't normally obsess over prices like that (I buy ready-made pigs in blankets at Christmas, for example, as life is too short etc), but I looked at the inventory, and thought "am I ever going to need all those 5-lever ones, or all those 6- and 8-hole push ones?" So, expecting the kit to be cheaper, I thought "well lets just see how little extra I'd pay to get all those compared to buying my own selection". I was soon surprised. And I don't need the organiser case.