BTC network analyses from miners viewpoint

this is not financial advise its just my thought about BTC network analyses from miners viewpoint
I am writing my idea about preparing a BTC :
If we use 4x Antminer S9i with 14 TH that we found around 800 $ ( 4*800$=3200$) we are able to mine a BTC after 1 years while all condition constant such as difficulty, power cost,Pool fee , ...
i assumed power cost 0.1 /KW and each miner use 1370 KW ==> according to the whattomine calculator after 1 years we just have 2200$ or 0.3259 BTC profit.
we can expect to have 12 Antminer + 1 years to make 1 BTC with present price.
12*800$ = 9600 $

assumptions :
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Antminer price = 800$
pool fee=0
power usage each device = 1370 W
difficulty = 4.94 T
Block rewards= 12.66
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