Koliko to košta? means “How much does that cost?” – a sentence that works in every shop and at every petrol station.
This particular shop shows its prices in an unusual way: a lump of coal is placed on the counter, and next to it another one – two lumps of coal give you koliko. When you pay, thunderous applause comes out of the loudspeaker, that is the to. And then you are told it still costs a lot: košta.
This sentence comes up constantly while shopping in chapter 3, so it is worth practising thoroughly here.