leasing is generally not going to be a deal you win if you are good at math / do research. car companies are good at math, they aren't giving you a deal they are just giving people more numbers to fill their heads with usually. anyway here is my 2 cents, its gonna be a long read hahah
when you lease they do calculate the residual and obviously that is how they calculate your monthly. and then they are conservative on this, so you lose on this transation unless residuals plummet in the say 3 years you own said vehicle.
for example, you lease a $20k car and they project it has a 50% 3 year residual on say 12k miles. its 3 years of payments + money up front is $10k. you just paid $280 a month.
of course you wont actually pay $280. since the car dealer is taking all the risk should residuals plummet to say 40% (and this has happened say in 2008 when gas prices spiked, SUV residuals were way way lower than people who leased in 2005 predicted and dealers got ass raped) they probably will charge you extra.
leasing is effectively insurance against a drop in residuals. so say they charge you $300 a month (instead of $280, because the $20 is the dealer insuring themselves of an unexpected residual hit etc) for a car with projected 50% residual in 3 years that costs $20k up front. assuming you drive exactly the miles you contracted for (which obviously factors into the residual) then you realistically are only paying them the $20 a month to put the risk on them should the residusal fail.
i mean think of it this way. if you could tell the future and knew for sure in 3 years the car would be worth $10k why wouldnt you just buy it now for $20k, and sell it in 3 years for $10k , drive it for 3 years the same number of miles as the lease, but give yourself the option of say keeping it more than 3 years, or less than 3 years (sya you get a way way better job and want to upgrade) while also saving $20 a month ($720 hypothetically could be more could be less i havent done THAT much research on how leases go with say a camry to know). if you could tell the future there'd be no point to leasing right? so leasing is just like car residual insurance. not leasing the car would also give you the option of exceeding a yearly miles quota if say your lifestyle / job changes. you can't really renegotiate a lease so you'd get stuck with the milage overages. buying gives you flexibility in length of ownership and miles used, but sticks you with the consequences of owning car longer / driving it more (i.e. more depreciation)
now a lot of people get fooled by things like money factors (which is basically implied loan interest... which can say be an implied 6-7% in a near 0-1% environment but many many people are really bad at math and dont understand this). so the one way you could get even more screwed on a lease is if car residuals actually go up while you own your car.
for example, i bought a 2010 A4 at the start of january 2010. at the time the lease residual on it was 51% for 3 years. so i just bought the car since i drive a lot of miles and wasnt sure i'd get a new one in 3 years. so 3 years go by and residuals right now are in the 58% range. i'd guess residuals are up because the economy is slightly better than after the horrible stock market of 2009, that and in my case, audi's desireability as a brand seems a bit more these days than 3 years ago.
So I happen to in fact be in the market for a new car, so given the weirdness in the used car market right now, i actually will do much better than the leases i could get in january 2010, by buying the car outright in 2010 and selling it now 3 years later. i calculated it out and ill probably end up better off by about $100 a month (just so happens to be 35 months or so ) compared to leasing a car with the type of milage i ended up using. so in this case not only did i not have to insure against prices falling, i actually got some upside on the rise in future used car prices.
granted i took the risk (like say if audi's started killing people randomly and residual dropped to 25% i'd be screwed right?) . on a lease, i would just turn it in and not had to do the math.
so yeah thats my understanding of leases. i know theres some tax benefits to leases as well as its easier to calculate if you own a business (instead of say writing off car depreciation vs, just your monthly lease payments) so there is that benefit of leases being easier to write off. but if you dont own a business well... i tend to think leases are really only good for people who will in fact drive exactly the number of miles on the lease and are really afraid of not winning on the depreciation front over 3 years.
leasing is just anothe rway to spin a dumb persons mind around with more numbers and options and it LOOKS cheaper because buying costs more up front. but overall i think leasing generally does not work out for people (at least smart people who do research, and like know how to do math / figure out depreciation on cars).
one point i can think of with leases that might pay off really well is if you buy say a 3 years lease on a car and that cars model changeover happens during your lease. not sure most leases account for this. but say you leased i dont know, a 2013 lexus IS. the lexus IS is going to be brand new next year and generally this causes a much larger hit to residuals than just a normal year of same body style. so if you sell a paid for 2013 lexus IS in 2016, itll probably take a larger hit, compared to say selling a 2010 in 2013. food for thought i guess.