It's wrong to be manipulative.
Bob is assigned a new client by his company, in hopes that he will improve their sales relationship.
Bob wants to make a big sale to the company.
Bob gives a strong presentation about what he has to offer and asks directly for more of the company's business.
Bob tells his new client that he can save them some money if they buy in quantity, but only for one day, which is not true.
The company he is working with appreciates his professionalism and rewards him with a large purchase.
The company finds out that Bob lied to them, when they talk to other people in the industry, and Bob loses all of their business.