I'm not quite convinced that cash up front has quite such a significant discount. Maybe if you are personally negotiating it with the dealership. Anyway I just wanted to point out better value financing can be had direct from OEMs/dealerships. After all, they make money from the car sale itself and don't have to make money from charging interest and fees as dedicated loan providers do.
That is where you are severely wrong! Car dealers aren't banks; the loans are outsourced to banks and they won't settle for a low interest rate. So the dealer has to make the profit from the car. Probably the dealer gets a kickback fee from the bank as well but guess who pays that... you!
You know these large OEMs are their own banks right?
https://en.wikipedia.org/wiki/Hyundai_Capital
Nope, it's StGeorge bank:
nctnico is right, you will pay for that, usually by not getting as good a discount as you can with cash. And doesn't include fees and changes.
So take a $50,000 ticket price car.
For cash you can pay say $46k and you are done.
For credit you'll pay maybe $49k (so you feel good you are getting some discount) and you pay at least a 1.5% comparison rate on $40k, so $500/year interest at least, that's $2k, plus fees and changes let's assume another $1k. So you've paid say $52k vs $46k, or $6k more than cash.
And if you have financial problems then you can't just sell the car because you don't own it, and you are still on the hook for the repayments.
But if you paid cash for the car, not only do you save a big chunk of cash, you can sell the car because you own it and can immediately recoup some cash.
Maybe the situation is different in Australia, or with different makes (I have only bought new Japanese makes that are known for not really negotiating much on price) but that has not been the case in my experience in Canada. Most dealers aren't really willing to give anything meaningful in the way of discounts whether you are paying cash or using financing. If there's a difference, it's small. There's a complicated relationship between the car maker and the dealership that I don't fully understand, but I believe the cheap credit is financed by the make, *not* the dealer, while any cash discounts they give you come directly out of the dealer's profit margin.
And your math ignores the time value of the money you don't have tied up in the car. Let's say you have $50k in cash on hand, and you draw from it to pay off the loan, so this is a self contained system.
If you pay cash, it's simple, the car costs you the $46k you claim you can negotiate it down to, you invest the remaining $4k for the 7 years at an achievable 5%, and end up with $4749.
If you finance and instead put the $50k in investments, 49k @ 1.5% over 7 years results in a monthly payment of $647.45. If you plug this into a 'savings calculator with regular withdrawals', and a compound interest of 5%, simulating investing this money at 5% and then drawing it down to pay the loan, we find a future value of $5673. This is considerably more than the $4749 you would be left with paying cash, despite the lower cash price.
Of course lots of people are irresponsible and buy cars they can't afford on credit, and buying a new car is not always going to be a prudent choice, but the point is that all else being equal, taking the financing is usually a better financial decision. It also gives you considerably more flexibility, since you have less tied up in an asset that has depreciated considerably and isn't all that liquid.