As someone who would need these services vs. supplying them, I prefer a model that charges a known minimum for the first hour "many things can get fixed in the first hour" then half hour increments + parts from there. I don't need to know how much it costs you to drive here. Build that into your first hour cost and let's be done with it. Any extra time can be spent providing value-add like checking for other almost broken things / cleaning the playfield etc.

I'd also love the ability to pay a somewhat reduced rate for a virtual diagnostic session over Skype / Zoom where I can show you what's happening to the game and you can give me a better idea of what my final bill will be to get it all fixed.