It's better to teach why a thing is good or bad, right or wrong rather than threaten or coerce someone into doing something.
To coerce makes the situation better in the immediate moment, but as soon as you're gone resentment begins to breed and your rules or ideas are cast aside with a vengeance.
To teach why a thing is good, bad, right, or wrong will help your subject to make the inner-decision to choose the right or good thing and that is a constraining force that is not only still effective when you're no longer around but will leave everyone feeling much better about the decision in the long run.
In terms of sales, if you undercut or offer "killer" deals to rope somebody into buying a product, sure you got the sale, but not the customer.
As soon as they realize what you did, the jig is up. Why do we all think car salesmen and lawyers are slimy? Because we never feel like we have the power to make the final decision due to the near constant manipulation that takes place in those transactions.
When your customer realizes why they should buy your product, they can make that decision and purchase what you offer no matter the price. They also grow to love you and your product instead of growing jaded and disillusioned to your machinations.
Teaching is better than tricks and threats.