This is exactly our philosophy when we travel. Since our first class air travel is on points and (typically) our lodging is on points our splurge is on guides and car services (and some restaurants) On this trip we had a private day trip with guide to Giverny, a private boat trip on the Seine in a beautiful Venetian mahogany boat, a private day trip with guide to Delphi, and a private sunset boat tour of Santorini. In a few days we will have a private tour with guide of the Palace of Knossos. These are experiences we will never forget.
We decided years ago since my husband will not sit behind the wheel after even a sip of wine, especially in a foreign country, that car services were the answer. And after calculating rental costs, insurance costs, and hassle, this seems like a bargain to us.