I found myself at Del Frisco's last week for a business lunch. Unfortunately, I didn't have the guts to pull out my camera and start snapping pictures of my food...so I can't prove I was there. But I did order the $13 prime burger and fries. You won't see it on their dinner menu, but I guess you can find it in the bar if you go at night.
I ordered it medium rare, and it came out juicy and hot. The waitress told me they use 100% tenderloin prime beef and grind it themselves, then broil it. My burger had a nice crust, and came topped with well-melted cheddar cheese. They've got some other cheese options that I didn't bother with because they weren't yellow (that's tongue-in-cheek...I like bleu, swiss, jack at times).
The burger came with a very fresh thick cut beefsteak tomato slice, some lettuce, and onion. Also included were some crispy ridged pickle chips dusted with some fancy pants green herbs. Wonderfully fresh produce.
Overall, the burger was cooked well, was juicy and flavorful, and a good experience. The first bite was the best, but I started to get a little bored as I methodically gutted the second half of the burger. That's my fault, though...I just don't think I was in a real "burger" mood (which they are no excuses for, and I berated myself for it).
If you've got $13 and need to schmooze some people over lunch, try the Del Frisco's burger.