We recently got a tire at the dealer. My wife got a flat while she was trying to get to work. The car comes with roadside assistance, and the "easy path" was to let them tow it to the dealer.

We could've done the work to find a private shop to change the tire and redirect the tow truck there, but it takes effort, my wife gets intimidated by car stuff, and she was busy with some work meetings (which she took at the roadside).

In the end it cost us an extra $100, but probably saved us $1000 of marriage counseling :) That's ROI !

Dunno the percentages but I see them advertise tires, so not zero at least. Saves you from a separate run if you have them installed during service.