It worked on standard low fares. If it cost $200 for a roundtrip ticket from SFO-LAX on United, and you traveled with a companion, you paid $300 out of pocket instead of $400. TBH, it was only really worth it if you bought very cheap coach tickets and traveled as a pair. The $100 savings became less valuable the more expensive your tickets were, since the opportunity cost of using the Ritz to buy airfare (vs a more lucrative card like Plat Amex) grew with the ticket price.