Their is no line between outright thieves, scammers, semi-dishonest hucksters and those selling cheapo junk with no service or support. It is a broad and blurry spectrum. If it seems too good to be true, it is.
As John Ruskin said 150 years ago:
"There is hardly anything in the world that someone cannot make a little worse and sell a little cheaper, and the people who consider price alone are that person's lawful prey. It's unwise to pay too much, but it's worse to pay too little. When you pay too much, you lose a little money – that is all. When you pay too little, you sometimes lose everything, because the thing you bought was incapable of doing the thing it was bought to do. The common law of business balance prohibits paying a little and getting a lot – it can't be done. If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that you will have enough to pay for something better."