Using Chase Ultimate Reward I found two qualifying items that have a 25% bonus so that would be about the same as using them for travel. In this case the ticket was 50 and a food upgrade was about the two charges her so I offset the cost of my ticket and food upgrade. If you want to be exact you can even do partial amounts but usually I just round up if I'm using points. NOTE: the red circle is the time limit so make sure you use before they time out.
I think the card that made this popular was Discover and they would original send you a check. I personally have both Discover and Costco right now that build cashback. The Costco card still sends a check but it can only be cashed at customer service at Costco. Yes, it's better to cash it and put your Costco order on the card again so you collect more cashback.