Running ads is difficult. There's clearly people spending huge amounts of money through online advertising and this happens because they are able to get results (understanding what works and what doesn't work on each platform).

Once they figure out how to get the results they need, they can put a dollar into Facebook and get more than a dollar out. Then they just turn the budget knob to 11.

Point is, those who make posts saying that Facebook is scamming people are just dipping their toes into advertising and will more than likely fail at first. Advertising online takes some investment to find out what works for your situation.