The charter fee generally covers only the hire of the yacht and crew, all other expenses are in addition to the charter fee.
These additional expenses are covered by the Advance Provisioning Allowance.
The APA is usually 30% of the charter fee (sometimes 35% if the yacht burns a lot of fuel or if you intend to do more than about 4 hours of cruising per day).
The APA covers the cost of fuel, food, wines and liquors, dockage, communications, etc. Any APA not used will be returned to you at the end of the charter as you leave. On the other hand, if expenses exceed the APA (maybe excessive cruising so high fuel costs, requests of rare liquors, etc.) you will be expected to reimburse the yacht as you leave the charter. This is rare but you need to be aware of this possible expense.