For regular stores with set prices, you could say:
* Do you have any discounts?
* Are there any discounts available?
This is useful if, for example, the company gives discounts for students.
Things are a little different if you are haggling.
* Is that the best you can do?
* What's the best price you can offer?
Or, if you are willing to get a different, cheaper version of the product:
* Do you anything cheaper?