Don't know about it being a licence to print money. At best a DPE can do one checkride per day. In practice there just aren't that many to be done. I would not want to try to make a living as a DPE (though people do, along with some instruction).
+1 on that. Getting two check rides a day is rare. Also, DPE's are (like flight instructors) often on standby because of weather, so that (s)he gets one check-ride for two days on standby
And, like flight instruction, DPE's appear to be more expensive in CA, FL and NY.
In the North-Central region, check rides are more in the $250-$350 ball park.
As Silvaire already remarked, $100/hour for a DPE is not exaggerated. But it must be enjoyable, because you get to teach from a privileged position to very motivated students.
