A couple of years ago, the Minneapolis-St. Paul airport introduced self-pay parking gates. Scan a credit card on the way in and on the way out, and it just debits the card. This obviously saves money on parking attendants, and it's pretty convenient for parkers.
At first, to encourage adoption, they offered a discount of $2 per day. Every time you'd approach the entry, a friendly voice from a Douglas Adams novel would ask, "Would you like to save $2 per day on parking?" For general parking, that meant $14 instead of $16 per day.
Some time later, this switched from being an incentive for adopting the system to a penalty for avoiding it. How? They raised the rates by $2 per day. So now, the top rate if you use self-pay is back to $16. If you don't use it, then your top rate bumped up to $18. Clearly they put somebody from the banking industry in charge of this parking system.
Now, it's changed again, from $2 per day to $2 per transaction. So it's just $2 off the top of whatever your overall parking fees are.
This gradual creep is really interesting. I wonder what the next step will be. A $2 per year discount would be one way to approach it. Maybe a "frequent parker" program. More likely the discount will drop to $1 per transaction, or it will just be discarded altogether.
That's OK with me, because swiping the credit card is still more convenient than exchanging cash money with a human anyway.
Besides, back when it was cash based, I always got tagged with the ATM fee anyway.