What you need to do is figure out your monthly cost per $10,000 worth of vehicle for a 36 month lease.
By doing this, you can compare any two lease deals no matter what car you're looking at or how much price difference there is.
Any lease that costs less than $135 per month per $10,000 worth of vehicle is a good lease deal.
If you get an average 5 year car loan and sell the vehicle after 3 years, your monthly cost per $10K usually comes out to between $175 and $200 including interest and depreciation.
With this simple method, you can not only compare lease deals, you can also determine whether it's better to lease or buy a vehicle.
For example, if the lease payment is $200 per month with no money down for 36 months on a vehicle worth $15,000, your monthly cost per $10k would come out to $133 ($200 divided by 1.5). This would be considered a good lease deal since it falls under $135 per month per $10K worth of vehicle.
Let's take a look at a real lease deal from BMW for the 2011 128i Convertible. I've highlighted the important parts needed to calculate whether this is a good lease deal or not.
This is a 36 month lease on a car with an MSRP of $39,000. The lease payment is $379 per month with $2,500 down and a lease acquisition fee of $725. In order to do a fair comparison, we need to add the down payment and acquisition fee into the monthly payment. We simply add them up ($2,500 + $725) and divide by the term of the lease (36 months). The additional amount equals $90 per month, so the real monthly lease cost is equivalent to $469 per month.
To figure out the monthly cost per $10,000 worth of vehicle, you divide the monthly lease amount by 3.9 (3.9 = $39,000 MSRP divided by $10,000).
The monthly payment per $10k worth of vehicle equals $120.25 in this example.
Since the amount is below $135, you can rest assured this is a good lease deal compared to buying the same vehicle and selling it within 3 years. The very best lease deals I've seen hover around the $100 per $10k mark. These don't come around too often, but you will find deals in the $120 to $130 range pretty regularly.
Now let's take a look at what this car would have cost if you were to finance the vehicle with a 5 year loan at 7% interest and sell it after 3 years.
Your monthly payment would be $781.90, so the total amount you would pay over 36 months would be $28,148. At the end of 36 months, you would owe $17,463.81 on the vehicle, but the car will be worth $23,010 (we used the residual value provided in the lease deal above). This means you will have built up $5,546.19 in equity.
To get your true monthly cost over this 36 month period, take your total payments ($28,148) and subtract the equity you built ($5,546.19), which comes out to $22,601.81. We then divide this figure by 36 months and we get $627.82.
Finally, we want to figure out how much this cost you per $10K worth of car. ($627.82 divided by 3.9) = $161.
With leasing, your cost per $10K was $120.25, saving you over $40 per month or $1,440 over 36 months.
Of course, these figures can change depending on the interest rate of the loan and the residual value of the vehicle after 36 months. Good lease deals usually have inflated residual values, so it's not guaranteed you would have been able to get $23,010 for the car after 36 months, resulting in an even higher payment.
On the other hand, your financing rate could have been lower which would lower the monthly figures.
This is a quick and easy way to see if your lease is a good deal or not. As long as it falls below $135 per $10k worth of car, you're looking at a pretty decent lease deal.