You rent a Volkswagen Golf from a reputable company at Ostrava-Mošnov Airport (OSR). The rental agreement says that basic CDW is included with an excess of 37,500 CZK (Czech Koruna). Current exchange rate (approximate): 37,500 CZK is about €1,500 or $1,600.
You are driving on the cobblestone streets near Ostrava's Masaryk Square and you cut a corner too tightly, scraping the entire side of the car against a stone wall. The repair bill comes to €3,500.
Because you have basic CDW, you are NOT liable for the full €3,500. However, you ARE liable for the first €1,500 of that damage. The rental company will charge your credit card $1,600, and their own insurance will (eventually) cover the remaining €2,000.
You just saved €2,000, but you are still out of pocket by a staggering $1,600. Your cheap rental just became incredibly expensive, and your vacation mood is shattered. This is the trap of relying on basic CDW.