Here is my interpretation:
It is a rephrasing of the saying "Money talks, bullshit walks" which refers to business deals and by extension to life in general. If someone commits money to a business deal then people will seriously listen to what he is saying. If a person does not commit money to the deal but only talks, then that person will not receive serious attention and will eventually walk away.
Money talks..... money has a strong influence on people's actions. It is a sign that you are serious about the business deal.
Bullshit.....empty words or ideas; nonsense
Bullshit walks.......bullshit is not serious and eventually the person walks away from the deal
sales talks, shit walks
"Sales" is subsituted for "Money" in your version. If the salesman makes the sale, he will talk the customer into buying or commiting his money. If not, his words are empty or "shit" and he will walk away without making the sale. So the expression means that the important thing for a salesman is "sales" or the ability to make the sale.