However https://hashfast.com/shop/babyjet/ is advertised as "As Low as $2.80 / GHash"
I know it doesn't include the electricity and hosting, but 350W, I can certainly handle it at home.
Could someone confirm my calculation?
The "as low as 2.80 per GH/s" is misleading -- they're counting the extra *chips* you will receive from their miner protection program *if* your miner fails to ROI. You will get those chips without the supporting circuitry etc., and three months after the date you receive your miner.
Edit: The 3 months in the future part is the real nasty -- hashpower later is not the same as hashpower today
It's certainly better than nothing, but i'm not sure how much protection that program offers. If the BOM to make those chips into hashing miners costs more than the coins you'll mine with the finished product, it'll simply put you further into the red.
I don't want to argue the point here -- simply answered your question.