The way that Invent Help works is very simple. They take your money ($700, $800, $900, etc.) and promise to show your invention to a bunch of companies.
They do show your invention to a bunch of companies, with no intention of getting you anything out of the deal. They tell you that these companies rejected your idea, knowing that there is no way for you to check up on whether or not they actually did. They figure that the amount that you paid is not enough for you to come after them for fraud, which is true 95% of the time. The companies that saw your product and liked it will go on to produce it and make money off of it.
They actually have a team of lawyers to shut down any claims that people make against them. They know that you cannot afford to go to court to fight them.
There are a few court cases that go the distance, but those are so few that they still make out great after all is said and done. The companies are just too big to be defeated.