Let me directly say, as a game developer, that this is not true. This line is fed by certain big companies who want to maximise profits and can’t stand the idea of anyone paying less than top-dollar for their games - and also really don’t want someone ELSE making a huge profit off their games.
If you buy a used copy of the game, then the original company selling the game made only one sale, but two people got to play the game. This is less good, for them, than if both people had bought the game at full price. However, many people buy games /knowing that they can resell them/ and therefore can afford to spend a little more on buying the game new, because they’ll get some of that money back. If I buy a game for $30 and sell it to you for $15, we each paid $15 for the game. You could consider that we joined forces to buy the game for a price that we could afford. If each of us could only afford to pay $15 for a game, then without the ability to buy and sell used, neither of us could get the game.
Now, yes, if that same used copy is passed from player to player and is resold three hundred times with none of that money going back to the seller, that’s sort of bad. It’s also sort of unlikely. If you want to be sure you’re not contributing to that, buy games that have only been used once, and don’t resell them again.
Obviously, if you CAN afford to buy a new copy, it’s better for the company if you do so.
Now, there is another way that used copies get sold, and this is the one that really pisses off content developers. Say you buy a new game from a store for $50. You play it and then you try to sell it back to the store when you’re done with it. They pay you a piddly $10 in store credit, then turn around and resell your used copy for $45 - just barely less than the cost of the new game. So not only are they reselling used copies, but they’re making a pile of PROFIT off it, and none of that money goes to the company that made the game.
Don’t buy used copies from stores. Buy them direct from players.