No I didn't contribute to the used game market. I don't buy used games cause number 1 they never work and number 2 I hate gamestop. I never said anything about buying the game used? So get your facts straight.
So what i quoted is coming from someone who bought Bioshock new but then sold it and is under the impression that he didn't contribute to the used game market. If you do the same with your games and under the same assumption you are misinformed.
The prices for the used game market follows the Economic Law of Supply and Demand , which you can read more about in the link. The law says as supply increases of a product the price of the product will fall if demand stays the same or decreases (few exceptions apply). As far as games are concerned if you sell a game you just bought after beating it, you are increasing the supply of that game in the used game market. By doing so the price of the used game will fall which will cause the price of the game NEW to fall also to stay competitive (lower price of course, lowers chance to make a profit), otherwise the demand for the game New will fall as the demand for the cheaper used game increases.
It's why games besides selling well, want to have high retention rate among those that buy it. It's why multiplayer modes are tacked on, DLC is promised before the game is launched, among other ways Publisher's hope to keep the game in your possession. It's why games like COD take forever to fall in price and go for quite a bit used, besides being popular most COD players keep playing the game until the next COD comes out. Low supply of used games and consistent high demand will keep the both the New and Used game prices up there.
This isn't me on a high horse telling you not to trade in your game if you beat it in week after buying it. If a game disappoints me like Homefront did last year, I have no problem throwing it on ebay. Don't assume that if you sell games which you have bought new your not contributing the used game market and having a negative impact on the success of perhaps your favorite franchise.
The best real world example would be the price for a barrel of oil. If their is or a potential for a disruption in supply like turmoil in Libya last year or war with Iran the supply will decrease at least temporary and the price will rise. Just as if OPEC dissolved and they didn't regulate their production and oil producing countries ramped up production - supply would increase and price would drop. In a world wide economic recession their is less production of manufactured goods which means less demand in the oil used to produce the goods which means a lower oil price. As economies turn around (as their are signs of now) or the seasons change going to Summer with an increase of driving means an increase in demand, oil rises in price.