I can't give you the price of Silk Cut, but I do know that tobacco products have increased in price this year.
Whatever you do, don't leave it till you get to the airport to buy ciggies, they are very much more expensive down there.
My Golden Virginia in the shops is 48 euros and at the airport was 63!!
If the shop is closed in Cala n Bosch, just go to the nearest town and find there Tabac.