guys, in your calculation i'm not seeing any reference of a customs fee, that in this case is a pain in the ass for a decent ROI. At least let's check that bitmain is declaring low values (like the amazing 120 USD computer gaming gateway

)
True ... last S2 I received was quoted as a 'Bitcoin Miner' ... well OK ... it is ... but please don't advertise the fact to UK Customs so they can have a little fun with their charges. The one before was a 'Computer Gateway', and cost me £125 less in fees!
All that said ... the S3 will be available way quicker than I thought it might ... will be interesting to see their pricing, how the upgrades work etc ...