You will never get your ROI on a mining machine unless you're in 1 of 2 buckets.
1- You own a manufacturing company who can house, operate and develop your own miners with minimal cost.
2- You have a secret relationship with "underground" miners who are running operations that the general public doesn't know about.
That's not strictly true - there are many variables that may allow a small-time miner to ROI. But it is a big gamble so I mostly agree with your overall assessment. Manufacturers are selling you a huge risk and pocketing risk-free money.