I have been to santorini this summer. It's an area which is not comparable to the rest of greece. A raxi to dea sunset during the afternoon can easily be 30 eur and we are talking about a distance of 7 km.
Maybe off-season it's affordable. But combined with Mykonos it's an area where the term highway robbery comes ro mind.
The roads are indeed super dangerous in my opinion (I rented a scooter once and truly feared for my life when huge buses lost their patience and overtook me during switchbacks, after that experience only cars!) and additionally you really need to be in amazing shape to bike there - steep climbs everywhere, under a hot sun.
Maybe off-season it's affordable. But combined with Mykonos it's an area where the term highway robbery comes ro mind.