Great topic.
Something not mentioned is the application and the distance from the servicing dealer. If Toyota is nearby- it lowers their cost for maintenance and repairs. This whole process starts with an application survey-hours, dust, operator training, cracks in the concrete, width and height of doorways, etc. Toyota looks at this and guarantees the residual(at least they did when I sold Toyotas). If the survey is honest then there should be no trouble when returning the machines.
Next, a tax lease (residual) price is determined. The dealer can opt to raise the residual - but they would be responsible for the additional cost at trade in time. The higher the residual, the lower the financed amount of course. You are only financing the difference between the sales price of the truck and the residual value of it at the end of the lease. Toyota always had great rates, so you have a low rate to finance with, and a truck that holds it's value well. These add up to a low lease rate. Two quick notes. You can package a purchase of the machine with a full maintenance lease. Makes a higher note, but you own it at the end. And my personal favorite for a mom and pop- very low hour use machine. Purchase with a residual lease without the full maintenance. Customer gets a new dependable machine, pays for 2 PMs per year, turns it in in 60 months. On this deal I would build in an EPTW so you get no surprises. OK, I digress...

Now, you have your price for the truck and usually the product support rep will work up the price for the full maintenance. Again, I suggest you roll the EPTW onto the cost of the truck, which gives the service department very little risk during the course of the lease. Other than abuse, very few non warranty repairs will be needed the first 2-3 years. Dealership pockets much cas$ if handled correctly. The last years will require more repairs, but again if managed well this is minimized. Keep tilt cyl kits, tune up parts, etc stocked for those trucks in the van.
Now, add the two prices together and you have a full maintenance
Price.
One of the dealership advantages is the ability to increase the profit margin a LOT by raising the note only a little on a residual lease. The other advantage is first access to lease returns that are well maintained. My finger is tired. Think I'll go home now.
Steve