What’s the secret to making a $35 mini computer? The basic recipe is having some extremely skilful cooks who can craft batch after batch of Raspberry Pis as quickly and with as few duds as possible. Sony’s U.K. factory makes an average of 4,000 Model B Raspberry Pi’s every day – or one every 7.5 seconds – and it needs to to keep up with demand for Pi which continues to sell like hot cakes.