If you are to buy the s15 contract from them and they charge you s15 power prices while mining with modded super efficient s17s they score and you have zero repeat zero ability to see the miners in play.
When people were getting s9s doing 100 watts a th bitmain had firmware that allowed for 82-85 watt mining.
Many large miners and farms had that edge.
Basically bitmain breaks endless rules of accounting and has no accounting external audits.
Or bitmain is full honest breaks no rules and is full audited via external audit companies they simply choose to not publish the audits.
Take your pick they still wield a mighty pickax in the mining world.
They make 100% sure they stay ahead. From the time you buy it or rent it you already lost these days. Plug it in "initialization fee" cash out %'s etc. It would be interesting to see a competitor come just on hardware value alone like graphics cards. Something that tries to follow Moore's Law. And is just 100% upfront.