- Edited
My first impression is @ShiroKuro's tuner basically means he'd do this simple job for next to nothing, and "gas money" is just a metaphor of any small amount. No need to really factor in the actual mileage he'd drive. 'Cause if the tuner really come to do this as a single job trip, he'd ask for a real amount to cover cost.
As for the tipping culture, I had to really learn it as an immigrant. Part of it is I don't want to be seen as the odd one out. But the other reason, as I gradually understand, is that not tipping sometimes stiffs the wrong people - the good ones. Encourage the tip is a sneaky way of business owners shifting their obligation of paying their employee sufficiently to the customer. But unless such practice is abolished, the employee is the one who gets hurt when customer don't tip. This is especially true for restaurant waiters, but in other service industries, too. This also means there is no need to tip anyone who is the business owner, including those who works for themselves.
But I also feel in recent years the tipping culture is getting out of hand. When I first arrived in America, I learned that you tip 15% at full service restaurant (20% if service is exceptional, and 10% if not satisfactory). Nowadays I frequently hear that 20% is the minimum! Some try to justify it with inflation. But inflation is on meal price too, which should make no change in tip percentage necessary. Also non-full-service eateries are showing a mandatory tipping screen at checkout counter, and some even hide or obscure the "no tip" option. Another thing that make tipping a real nuisance is you often need to have cash in small change.