You probably already know that. But recent sales data collated by Gamasutra shows just how badly the company needs your used games, with preowned sales accounting for a ton of the company's gross profit margin.
See for yourself in the graph above, which shows that used product sales - which combines the sale of preowned games and consoles - make up 48c of every dollar of the company's gross profit margin (which is "the gross profit divided by total revenue").
You all keep whining at the low trade-in value of your games at GameStop, and yet, you all keep trading your games in at GameStop...
There's more information (and more coloured graphs!) at the link below.
In Depth: The State Of GameStop, Part One [Gamasutra]