I think you'd be surprised at the resources needed to create games these days. Budgets run at tens of millions even for the cheap and cheerful. The really big names run to hundreds of millions. They're by no means a guaranteed cash cow. Most new games, in fact, make a loss, which the publishers try to offset with their blockbuster cash cow titles.
That aside though, I agree it costs a lot more to make a car, and therefore follows that it should cost a lot more to buy one. That's not what I'm arguing. It boils down to this:
The used games market provides a method for someone to sell a brand new product, at no loss to themselves, for 2/3 the sale price available to the creator of that product, regardless of the sale price set by the creator. The creator is, therefore, stuffed. They can't beat the competition on price.
Proof:
Assume games sell new for 60, resell for 40 and are bought used by the retailer for 20. Assume the retailer makes a hefty 66% profit on new games (not far from the truth either. They make the big bucks).
Customer X has 60. He buys one new game a month. 20 goes to the publisher, 40 to the retailer.
Customer Y has 60. He buys (and re-resells) 3 1 week old games a month, at a total cost of 60 (40 * 3) - (20 * 3). 0 goes to the publisher, 60 to the retailer.
They essentially shift ALL of the profits to themselves, rather than share it with the publisher, and it's rather attractive to the buyer too. He only has to wait a few days to get a nearly new game.
This is the point I'm trying to make. You're right that no-one would want a six month old used game, but the problem is that a few days after release people will start trading in their games, so the market is undercut. Games are therefore MORE likely to be bought used. Why not? They're basically identical to the brand new version in everything except price.
This market undercutting can't be done with cars because there's no ready supply of used cars available for a significant period after a car is launched. Few people are rich or crazy enough to trade in their brand new car. A couple of years down the line the market will appear but the car manufacturer doesn't care (too much!) because they've got a brand new model out and everyone wants that one now. They still have a market. If we could buy cars for 50 quid each car manufacturers would have the same problem.
Books and CDs are an excellent example of similar markets to computer games which don't suffer from the same problem. I suspect that's because they're cheap enough that there isn't enough profit in it for the resellers. Unfortunately you can't just drop the price of games down to book level because the cost of development is significantly higher.
So, solutions:
Reduce the development costs of games? Fine, but you can't do that without sacrificing either quality or quantity. Not what any of us game buyers want, right?
Add on-line purchaseables that are so good people will just HAVE to buy them? The slight problem with this is that publishers and developers are amoral, capitalistic, companies and will take the line of least resistance to maximum profit. When you jack your first car in GTA 10 a screen will pop up asking for your credit card details. And again for the second. And so on. Essentially this is a form of DRM which locks out reselling, because the game's unplayable without an injection of cash.
On line monthly sub or pay to play of some variety? Well, yes. That's about the only workable solution, and effectively anti-resell DRM again.
Essentially we're screwed! Not buying resold games, however, gives developers one less reason to go down this road, and allows those developers who want to be a bit more moral about it an avenue to do business. It's not capitalism, but what can you do?