When faced with a decision, our brains look for information in all kinds of places to determine whether we are facing a good choice or a bad one. In the case of judging prices, we will subconsciously refer to the last numbers in our short-term memory to make our judgment. This is called Anchoring.
Setting quantifiable anchors in the short-term memory of a prospect will cause them to consider not just the price of your product or service, but also how that price compares to the anchor. That comparison will be used to judge whether your price is reasonable. Setting an MSRP is an example of anchoring in the retail and e-commerce industry. Even though nobody ever pays the MSRP, this price is still taken into consideration during the buying process.
If you are running a service business, you can use competitor pricing or industry average pricing in order to provide an anchor for the price of your own services. If you charge a premium and avoid running discounts or keeping prices low (such as a luxury concierge service), anchoring will be difficult (and possibly off-brand) for you.