I think the question was implicitly about a different issue. Why is the BOX processor cheaper than the MPK processor?
I don't know. It should be otherwise. Perhaps (I speculate) the MPK package includes cooling, which is not in the box.
As they taught me once in a course in practical economics, if you want cheap, buy only what you want, without free extras that you will not be satisfied with. Ergo, if it's a processor, then a processor counts parameters, frequency, cores, technology, etc - the packaging can be OEM or whatever. What is the advantage of BOX? Well, there is an installation manual that you will not find in the OEM, but you can look for it on the net.
Added after 6 [minutes]: Ha ha ha... exactly
MPK = multipack, i.e. instead of one processor you buy several pieces.
Theoretically, because some stores sell MPK - i.e. multipack - fan radiator paste procek