Context #1
Jim: Wow! Look at the ticket prices for the Jay-Z concert. The cheapest tickets in the seats way up at the top are over $200!
David: That's a ripoff!
Context #2
Sara: I need to get my oil changed, but the place I went to was going to charge me $100.
Christine: Don't do it! That's a ripoff! You should try somewhere else.
Meaning: "ripoff" is a noun, and it is used for any time something is unreasonably expensive. Sometimes it's because something is just too expensive, and sometimes it's because people are being dishonest and trying to take money from the customers or consumers.