Food and drink prices at the less popular spots have cheaper prices. Anywhere that is a highly popular area for tourists is likely to have higher prices. The closer you get to Porto Cervo and Costa Smeralda, the higher the prices are going to be. The prices in markets are typical and wine and liquor tend to be cheap.
 

12 euros for pizza or pasta 
7 euros for a carafe of house wine
4 euros for small beer 
65-85 euros for a meal for 2 with drink (even some cognac and limoncello)
142 euros for lobster tagliatelle for 2 at an upmarket restaurant without a second course
63 euros for suckling pig for 2  
7 euros or more for cocktails
1.5 euros for a coffee
4.5 euros for wine in a supermarket