Examples:
* "That new car will set you back a pretty penny."
* "The vacation to Hawaii set us back $5,000."
Other meanings:
While the most common meaning is related to cost, "set you back" can also be used more figuratively to mean:
* To delay or hinder your progress: "The traffic accident set us back by an hour."
* To cause you to regress: "The injury set him back in his training."
The context usually makes it clear which meaning is intended.