Milk to yoghurt to cheese

Yesterday we had a 500gram/16oz tub of yoghurt that cost $3.50 and turned it into two litres/quarts of yoghurt that cost about $4. One litre/quart of that was eaten as yoghurt - with one cup reserved to make the next batch, the other litre/quart was made into quark cheese. Quark is a simple fresh cheese that doesn't require any special equipment and will be ready for eating as soon a you finish