Mac Tool Question ?

I bought a Sears small 4 drawer tool box with tools (1/4 inch, 3/8 inch, 1/2 inch) sae/metric sockets, and an empty drawer for open/box, screw drivers, etc. It was marked down over 70%. I asked why the mark down? 3 sockets missing. I said why not just take 3 sockets off the tool rack and put them in the "set", then mark down the set 10%? Answer, "we are not allowed to do that". I bought the set and the sockets it needed, and saved a bunch. No wonder Sears went bankrupt.