I've done the trip four times and have gone four different routes. The ferries are the high cost, as are the tolls if you go through France and drive on their excellent motorways.
Crete to Pireaus is obviously a must but then you can either drive north or cross over to Patra and take a ferry to Ancona, Bari or Venice. I've done the drive north and wouldn't recommend it unless you have time and a second driver to share the drive ie take the ferry from Patras to Italy.
Going the Italy, Switzerland Germany route is probably the cheaper option and if prepared to drive 10 hours a day you will only need one hotel night. The Italy France route is probably shorter but again it's at least one hotel night and the toll roads will cost around €120 over and above.
Both routes offer great scenery although the north west of Italy is busy and the drive is a little more tiring because of the traffic and windy motorway, multiple tunnels etc.
If you have time, and since you are retired you should have a bit if this, then plan your route via places you might want to see. Last time we went was in March and we took the Patras ferry to Bari, crossed Italy to the western side and spent two days / three nights in Pompeii and Herculaneum. The experience bettered my childhood expectations. We then drove north, spent a night north of Cannes and then a further night in Metz in northern France. My Great Uncle died there in 1913, killed in a car crash - he was the chauffeur!
I'm sure others will give you detailed plans but my advice would be to check Tripadvisor for well reviewed hotels and enjoy the trip because at our age there is little point driving non stop and missing out on the food, the wine, the sights!
We need men who dream of things that never were.