I've seen some other sources mention that the new minimum wage is actually "$27.86 an hour, which translates to $17.22 after expenses". [1]
What they consider "expenses" there isn't specified, but that would put their estimate for driver costs at over $10/hour. Which actually seems more reasonable, given the cost of fuel.
"The equivalent wage for drivers, who are considered independent contractors and have to cover their own expenses, is $17.22."
It's up from 15$ baseline so I assume 2.22$/hr is what they benchmark fuel/maintenance to cost.