I reserved a rental car in Crete with National Car Rental. The quoted rate for the car was 94 euro for three days, with pick up and return in the airport. When we arrived at the airport to pick up the car, they confirmed the rate, but then informed us (for the first time) that we either had to buy the insurance or authorize a charge of 8000 euro on our credit card (the full price of the car!). Obviously we chose to purchase the insurance, which raised our rental costs by 40-50 euro.
Since arriving home, I have contacted National Car Rental and been informed that this deceptive practice is apparently sanctioned by the company. I have filed a complaint with the company and requested a refund of the amount we paid for the insurance, but am not hopeful about it. So my advice to.you if you plan to rent a car in Crete is to ask specifically about insurance and required deposits before you rent the car when you are making a cost comparison. We saw lots of advertisements for rental car companies who claimed that they do not require a deposit or insurance.