Bravo Jack ... unfortunately you weren't lucky with the weather, but tomorrow it should be improving. I'm glad you came to Sardinia .... September is the time when many Germans and Swiss come. Many come in caravans with motorcycles.
Are you leaving from Olbia?
You're right ... and I'm sorry about that. Unfortunately, for some years now ... the tickets for transport by ship (for those traveling by car) have increased a lot and those by plane have decreased and therefore the rental companies including taxis, have taken advantage to increase the prices a lot prices.