i checked yearly chart of S7, and saw that a lot of GHS were bought way above then the current market trade, also if u order S7, and sell after 72 H of hash to market you loose 0.3BTC aprox.
I don't understand either why people still order Ant S7 for $370 (their number is stock desreases) whereas they can buy the hashrate at current market price with 30% discount.
Also I've just recalculated PPS payout for S9:
Current total hashrate: 2,812,940.6 TH/s
Blocks per day: 144
Average block reward: 13.5 BTC
So S9 revenue is 12.5 * (1 / 2,812,940.6) * 144 * 13.5 = 0.0086386467 BTC = 7.789 USD (at a rate 901.7).
S9 maintenance is 12.5 * 0.21 = 2.625 USD per day which means 33.74%.
Daily earnings 5.614 USD which is 0.3% (if Ant S9 price is $1699, current market price is 0.00015560 * 12500 * 901.7 = $1753.8, which is 3.2% higher).
Days to ROI: 303.
By the way, calculating maintenance ratio for Ant S7 is quite easy as it depends on the same ratio for S9. It is (0.445 / 0.21) * 33.74% = 71.5%.
Daily earnings for 4.86 THs of S7 hashpower are $0.8656.
Market price of the same hashpower is $256.8
Days to ROI: 297.
But if difficulty keeps increasing 15-18% per month as it did recently, S7 will go below trash level in 1.5-2 months, so they won't pay out unless BTC price surges.