I belive I saw some posts on webhostingtalk or some other forums that stated, that their method of operations is to buy tons of hardware - single platform (mobo) that they build their offering on - with greatly discounted prices from manufacturer. They will provide it for a year or so, and then they will create new platform again after a while after they are out of stock, this happens once every year I think. Also keep in mind those are not "server grade" components so don't count on expansions to the servers/ECC RAM - this kind of stuff - you want to scale - just buy more boxes, there are upgrade possibilities, but they are limited to my understanding.
It's a promo offer, they will only offer a limited number of them, and in few months introduce a better one.
Also I've been given faulty hardware at Hetzner and the support was quite ass-hatty. I said fuck it, replace the drive and reflash the OS, but they no, the RAID must rebuild. At the end of day, MySQL was still crashing under a heavy load, but that could have been software problem, not sure if I can blame Hetzner. What I didn't like, if you open the contract eg on 15th, then cancel a month ahead, eg on 10th, they will still bill you till the end of the month, 15 more days. They're still one of the best non cloud hosts though.
edit: now I remember - they actually insisted on the faulty drive (that I reported based on mdstat logs) to be hardware-checked in the machine while the machine is offline. Mind you, this drive was faulty from the get go.
I had two failing drives in my Softlayer box (was about three years after they were put in service ... so not bad), and Softlayer insisted on running the HD diagnostics on our machine taking it down for an hour.
We just ended up purchasing a new box, migrating over and letting them take the old one offline. We ended up paying less per month for twice the specs...
As long as the price > operating cost, they'll eventually make money on it. You could say that they take a different approach to say Rackspace or Softlayer which try to recoup the initial investment during the first month.
In 3 years time, they'll still be selling these machines. A lot of companies still offer the Xeon's 3220, which, if I'm reading wiki correctly, first shipped in Jan 2007.