How do they do it?

Bought this new Cistern for our Loo. The old one was 20 years old and leaked all the time. Must have cost us a fortune on water bills!
In our local DIY store they had these on offer, own brand, 12,95 Euros. Fitted now, works a treat. Came complete with all fittings, most of which I didn't need. I had a quick look at prices and the seperate accessories, taps, unions, pipe etc, cost more than the complete unit. How do they get the prices down so low? Quality was good, important bits were brass, the rest stabile plastic. Thanks Hagabau!!