You're not half as annoyed when you get a $25 parking ticket as you are when the fine is $50.
An investment banker isn't twice as excited about a $20 million bonus as she is about a $10 million one.
There are threshholds that determine how we feel about money-related events (good and bad), but beyond those threshholds, the relationships get all out of whack. Being a million dollars in debt feels about the same as being five million in the hole.
The way you feel about more (or less) of something probably doesn't rise or fall based on how much it cost to produce that feeling.
Marketers and organizations and the less emotional use this fact against us all the time. They understand that while the utility curve for money for a single individual can change widely over time, the value of that money to the organization is largely linear.