Providing that documentation and the components is a non-zero cost.
Not suing people for repairing or tinkering with your hardware is also a "cost" I suppose if you want to phrase it that way, because of the lost revenue you would have gotten from locking down the market and only providing overpriced replacements yourself. It's a cost in the same way that a law against stealing purses imposes a "non-zero cost" on all of us, since we don't have that potential source of revenue available to us anymore...
Components? Sure, but you bake that into the cost you sell them at. You're already buying them in massive quantities, so let repair shops order some from you - nobody is going to complain about having to pay x% over cost of materials to cover your expenses.