If you are wanting to provide bulk pricing, tiered pricing, or price breaks at particular quantities, then try one of the approaches listed below.
Commerce Price Table
A staple module for tiered pricing is Commerce Price Table module. It allows you set pricing for a product based on the quantity purchased and also gives you a nice formatter for displaying the tiered rate breakdown. For instance, you can create a product which has the following pricing:
One important thing to note is that the discounts here are site-wide, and are not aimed at a particular user or role/group.
Check out this Commerce Module Tuesday video for more details and to see it in action.
It is also possible to create tiered pricing with rules, but acting on the
calculating the sell price of a product event in Rules. Using this event, you could create a rule which looks at the quantity of products, and set a multiplier value based on the quantity of products in the line item, and then multiples the base value by that result, creating a discounted rate. However, it would be up to you to notify the customer of any discounts, since this would just be a rule.