I assumed their cost per mile included maintenance which is pretty standard to do.
To do 2 year payback would be 400k miles a year, which is impossible without nearly 24/7 driving, which could be possible with automation but unlikely they are figuring that.
Those truckers you linked are saying 10,000 a month is realistic without pushing it for long haul OTR so that 120k a year still at least 7 year payback.
The TCO includes the cost of the lease, so it already includes payback of the upfront cost. If you're not leasing it, your cost per mile without considering upfront cost is much better than even the TCO calculation shows, so you can "payback" relatively quickly. If you lease it, you can take advantage of the lower cost of operations immediately.
To do 2 year payback would be 400k miles a year, which is impossible without nearly 24/7 driving, which could be possible with automation but unlikely they are figuring that.
Those truckers you linked are saying 10,000 a month is realistic without pushing it for long haul OTR so that 120k a year still at least 7 year payback.