Roadside sales are mostly private cars, passing cars and the like. And you need to change trains or something, which is very unstable. Of course, the price will be about one third cheaper, so you can bargain.
If you want to buy a cheap ticket, go to Fengze Bus Terminal, which is next to it. For the sake of time and safety, it is not recommended to buy. If it is to save money, you can consider it.