The way they do it is that they're in bed with this calculator (which is the top result if you search for cryptocurrency mining in google):
https://www.cryptocompare.com/mining/calculator/eth?HashingPower=80&HashingUnit=MH%2Fs&PowerConsumption=140&CostPerkWh=0.12
This calculator does not adjust for the block difficulty increase, which is almost constant and can be easily predicted, instead, their calculation is correct for the first day only. And they just multiply that by 7, 30 and 365 to calculate the returns for weekly, monthly and yearly mining respectively. That's absolutely not correct, and would not happen.
My payouts decrease by 20% in 10 days. if it goes like this I will end up with less than half the either I would've been able to buy on day one for the same price as the mining power I purchased. You might be able to make profit in dollar terms, but your profit would be far larger if you just buy the currency you're mining and just sit on it.
I emailed them about a refund. and I got this reply:
"We are sorry to tell you that we do not accept refunds as stated in the clause 4 of your signed agreement. We do not issue refunds also because we have invested your payment in mining infrastructure. Investing in cloud mining is not without risk and we expect our customers to be aware of that and do their own research before purchase.
Thanks for your understanding. "
I guess that's some money down the drain.
This was your decision to buy ETH mining contract. Ethereum is transitioning to PoS, time bomb is already in place and doing its job. Moreover, total hashrate increased twice in the last month. There is almost no chance for ETH mining contract to ROI. 100 MH/s 2 year contract will earn something between 3.4 (if ETH price soars) to 7.5 (if price remains the same) ethers and will not fully ROI (in ETH at least, maybe in dollars you will get your ROI).
This is not because GM is a scam, this is because you should do a research before buying.