Am I doing the maths correctly ? Mining earnings

I will start mining Burst as soone as I have receive my new order, a 8TB seagate iron wolf 7200 rpm.
I figured out, not after a long time, that it wouldn't be sufficient in terms of earning. As most part of the energy consumption comes from the computer itself, not the HDD, and since they bring you the Burst, it makes a lot of sense to have the most HDD as you can afford.
I was doing some simple math here.
The cost of the electricity in Switzerland is 0.245 per kw/h.
I checked on http://powersupplycalculator.net/ and my computer consums 69 W in idle, 214 W load power (playing 3D games).
So let's say for the sake of the example that it is 120 watts, multiply by 24 hours and 30 days, it gives 86.40 kw/h per month so the bill for mining would be roughly 22 usd per month.
Now, based on the http://burstcoincalculator.com/, I should earn 2165 Burst coin per month, @ today's rate 0.052, deducting the electricity bill, I will earn a net profit of 95 usd per month.
 Can I assume that the consumption would be around 120 watts per hour while mining or would it take more ressources ?
 Is the website http://burstcoincalculator.com/ optimistic or realistic ?
 Should i take into consideration the pool fee or is it so immaterial that I can discount it ?
 Anything else I should take into consideration ?
Thanks !

PS: The profit I have mentionned is for 18 tb, not 8.