With all the recent media coverage there are many newcomers interested in mining that lack the experience or technical knowledge to design and build their own rigs
The best advice would be... "don't". At $2000 for 1800KH/s, at $0.18/kWh, 5% diminishing return each month for diff increase (ya right), over 2 years to pay off the device.
Miner telling other miners not to mine... You are assuming in your calculations that the exchange rate of all crypto coins will stay the same over 2 years. There were numerous times when bitcoin was under $50 that people made similar assumptions and said "it's not worth it" and "don't bother". Then there are the crypto coin millionaires. You are entitled to your opinion, but there are more appropiate threads to voice them in. Let's try to stay on topic here. Thanks