I totally get it, it really feels like gouging but imho having the car is priceless. There is so much to see and do on Oahu and the car gives you freedom to experience beautiful new places everyday, at your leisure, arriving and leaving when YOU want , not when the tour needs to leave. Ko Olina is kind of isolated and sure, you can do tours but they are going to cost you way more than that parking fee. One thing about your having made a cash reservation is that you do have the chance of being upgraded whereas if you were to have been able to book the DVC room that would not happen. I believe the DVC member who rents would have to rent you more points for you to move up a category. The first time we went to Aulani we split out stay between a direct cash ressie in a hotel room and a DVC studio stay. We were upgraded from a standard view hotel room to an ocean view. We really went not in the room enough for it to make a difference but it was nice to be able to look outside to the ocean. I am a glass half full type of person, so who knows - you might luck out with an upgrade that would be a trade off for the parking...