For people born in certain countries like China, it is indeed a bad deal, due to per-country quota. Yes, there are scams. A Chinese attorney couple in California got busted.
USCIS mandates that the investment (in this case, $500K) should be at risk.
However, if one has $1M to invest and create 10 jobs for two years, this pipeline hasn't exhausted per-country quota as yet. The GP makes enough money to go through this route. Buy a failing business in some area, run it for a loss and get the green card. Here, one doesn't need to deal with sleazy lawyers.
$7.25 per hr is the min wage in some states. $20K per year per job. 10 jobs per year = $200K. Run it until conditions are removed for the green card. Due to delays in gc processing, add one more year to 2 years conditional period. So, 3 years in total. The total cost: $200K * 3 = $600K.
