I often have a perfectly respectable bottle of fino in for cooking purposes which I get from my local supermarket for under 3 euros. One great thing about sherry in the kitchen is that it won't go nasty and acidic as a dry white wine would once opened, but will fulfil the same purposes. Deglazing anything that's been left to go nice and sticky and caramelised in a frying pan with a generous glug of fino is a real treat for both nose and palate.