If you guys think cost is going to make Bitmain stop you're all wrong. They have more than enough money to do anything they want. They made more profit than NVIDIA in 2017... They just made ASICS for Cryptonight which was deemed asic resistant. If the only factor is money then for sure they are mining secretly with their Asics. The only moment it was revealed that they had ASICS was when Monero announced their hardfork to change their POW.