Some anecdata, I buy midrange cards and never try to sell them. They usually end up in the machines of friends or family.

The purchase price is what I am willing to spend on the device and it's usage, and a healthy dose of pragmatism about what is actually necessary.

I also overclock to stretch their usefulness out but I must admit the leaps in each generation recently, as well as some fundamentally new technology capabilities mean I am not keeping up as well.