Četvrt kile sira means a quarter kilo of cheese.
There is a promotion at the cheese counter today: buy a quarter kilo and you get a model jet, which is valuable and weighs almost a kilo. Jet, valuable (wert in German) and kilo give you četvrt kile – note it is kile, not kilo. In the cockpit the pilot is smiling, and the seatbelts open quickly: “quickly” (rasch in German) gives you sira.
Pay particular attention to the endings here: kile instead of kilo, because a quantity comes before it.