I'm almost ready for my private pilot checkride, and it seems to me there is a perverse incentive for DPEs in passing or failing people.
If a DPE makes additional money on re-checks for students who fail the checkride, then it seems to me that DPEs have have a strong financial incentive to fail people the first time so that they can collect additional fees on the re-test. In fact, it seems that there are no rules in place to stop a DPE from making a student do the checkride 4, 5, or 6 times and collecting additional money from the student every time.
The checkride fee is exorbitant ($900 here in Southern California), but I'm even more concerned that the DPE would be hoping to fail me so they could collect extra money from me on a re-check. It actually makes my blood boil just thinking about it.
I'm not saying that DPEs are bad people, but the incentive structure certainly seems to make it easy for them to exploit eager students, and if economics has taught us anything, it has taught us that people respond to incentives.