In this scenario, at the end of the 4-year evaluation period, you want to keep the vehicle.  So, if you had purchased the vehicle, you do nothing, and if you leased the vehicle, you will purchase the vehicle at the end of the lease period for the residual value.  The vehicle has a current value of $15,000, which is equal to the residual of $15,000.

Let’s assume that if you purchase the vehicle you will finance the purchase.  The costs to purchase are shown in the table below.  You will have a down payment of $602.48 plus 48 monthly payments of $693.40 each.  Your total cost to purchase would be $33,885.68.

Total Cost to Purchase

Down Payment
$602.48
48 Loan Payments @ $693.40
$33,283.20
Total Cost to Purchase
$33,837.20

The cost to lease are shown in the table below. You will have an initial lease fee of $602.48 which includes the first payment. You will have 47 additional lease payments of $404.98 for total payments of $19,636.54. We then assume that you buy the vehicle at the end of lease for the residual amount of $15,000. You have now spent a total of $34,636.54.

Total Cost to Lease

Initial Lease Fee
$602.48
47 Lease Payments @ $404.98
$19,034.06
Subtotals
$19,636.54
Residual at End of Lease
$15,000.00
Subtotal
$34,636.54
Less: Interest on Invested Cash
$799.34
Total Cost to Lease
$33,837.20

However with the lease you will have excess cash each month. Your monthly loan payment is $693.40 but your monthly lease payment is only $404.98. If you lease, you will have $288.42 in extra cash each month. We assume that instead of spending the money, you invest it in something conservative like a money market fund and earn 3% interest. If you do this, you will earn $799.34 in interest over the 4-year period, which reduces the total cost to lease to $33,837.20.

The cost to lease of $33,837.20 and the cost to purchase of $33,885.68 are basically dead even. Since the buyout is equal to the residual, it would make sense that the two scenarios are basically equal.

Summary

Under this scenario, the results are the same. Neither leasing nor purchasing has an advantage. In general, anytime the value is equal to the residual, and you want to purchase the vehicle, leasing and purchasing should be about equal.