Making money via advertising while losing money on the deal…

I am flying to Washington DC tomorrow to attend (and speak at) the TANA 2007 conference. While I was booking my car rental at CheapTickets.com (Yes, I work for a startup) I saw an ad for HotWire.com.  Here is the image

Of course, the price at HotWire was cheaper than CheapTickets.com and I had no choice (again, I work for a startup) but to book my ticket with Hotwire.com.

I really don’t get it. Unless CheapTickets.com and HotWire.com are owned by the same company, it does not make sense for CheapTickets.com to send me to a competitor site. Yes, they made money through advertising but lost money on the deal 🙁