There was a guest lecturer at my university who gave a talk on distributed development who claimed there's been studies that have shown developers don't tend to get happier the more they are payed as long as they aren't payed too little. Instead they seem to value things like training or just staying challenged as opposed to money.

I'm sorry I don't know exactly what studies he was referring too, but I'm highly inclined to believe what he was saying and it would agree with what you are saying.