Because they order 128 the day a new instrument is anounced and have deep pockets.
I have been following developments at BGI over the past three or so years and was as stunned as anyone else at their announcment of a 128 HiSeq 2000 order in January of last year. 128 instruments was a lot then and is still a lot today. Certainly the largest sequencing centre in the world and significanty more capacity than every country in the world except the USA and UK.
BGI has 137 HiSeq 2000s as well as 1x 454, 27x SOLiD and 1x Ion Torrent according to the google map of next gen sequencers. The US has 712, the UK 132 instruments each respectively.
Using the latest 600GB run chemistry they can put out 50Tb of data per week.
A recent Newsweek article profiles what is going on today over in Shenzhen. Note this BGI is nowhere near Beijing. It also specifies a price of just $500,000 for the HiSeq 2000. I thought $700,000 was nearer the mark so this represents about a 30% discount. Pretty good.
Now all anyone else need to do to realise a similar discount is spend $64M in a single purchase order. Reagents not included!
Roll on HiSeq version 2... ;-)