Not sure if this helps but here goes:

When we bought our boat she was in the North Eastern Adriatic coast of Italy.

The best price we were quoted for road transport was by Van de Wetering - a Dutch company that do a large number of trips from North West Europe to the Med and beyond. there prices are good as they tend to manage to do return trips with a load rather than having to cost in for being empty.

For a 24 ton 44 ft motorsailer, we were quoted €7000 to be transported from Portorz in Slovenia (their nearest pick up point to where we bought the boat) to Breskens in Holland (the nearest point to us on the other side of the Channel/North Sea).

We chose the other side as it costs a fortune for a boat on a trailer to get from the Continent to the UK.

You will see from their website here that they do have destinations in Greece.

D