As there are many types of coffee, there are also different prices.
The cost of Italian coffee varies: about € 0.50 at coffee machines (not the best quality though), € 1 al banco (standing) in a cafeteria and € 1.20 if you’re sitting.
Of course prices are much higher in touristy places such as Milan, Venice, Rome.
Also, if you wish to add any ingredients like gelato or grappa to your coffee, this may cost a bit more than the usual espresso.