Earlier quoted context omitted.
I'm not sure that I did. If you are trying to compete in business X, you have a side income Z, and everyone competing in X has to buy service Y, what tangible benefit do you get from Y and Z being the same thing? Unless you can rig the bidding process I don't see any advantage.
It means that any expense you spend on Y isn't really an expense, since the money goes right back into your pocket. So not only do you get the extra income from other people buying Y, buy you can operate at higher margins than everyone else in X because Y is available to you at cost. EDIT: On further thought it seems no different than being vertically integrated.
If you do the accounting in this way, then you make that much less profit on your service, so it winds up being the same as if you are making a greater profit, but count the cost of Y at market value.
> So not only do you get the extra income from other people buying Y, buy you can operate at higher margins than everyone else in X because Y is available to you at cost.
This isn't any different than if Y and Z are different, but you use the excess profits from Z to subsidize your business in X.