I guess that's mystifying? There really is a SP silent majority in most game genres. Any examination of sales #s vs multiplayer activity makes this apparent, even if your own experience does not.
So you have both accurate sales figures and multiplayer figures? Where did you get those?
If DeadlyShoe had had those figures, DeadlyShoe would have said "80-90% of the purchases for dom3 are majority SP", rather than "it's almost guaranteed that 80-90% of the purchases for dom3 are majority SP". Words, mang, words