Extortionists.
When you take the City of Art tour, be prepared for unexpected expenses, and quite significant ones. The tour does not include: headphones for rental excursions for 25 euros, a boat to Venice for 25 euros (without paying, you will spend the whole day on the shore), hotel tax from 1 to 4 euros per day, mandatory (!) Tips for a tour operator, bus driver and accompanying person 15 euros, etc.