Paul....
My Weber gasser can reach 700? on a sunny summer day with little wind. My cooking partner has a Fluke Thermo that measures high heats accurately to like, .000000001. You really only need to hit around 500? to properly sear. But if the needle is buried, you will be fine.
Dennis......
Leave it to a fellow cheesehead to add the butter!!! LOL I ALWAYS add a dollop of butter at the very end to both steaks and burgers. Also, be sure to butter and grill those burger buns!
In regards to crispy exteriors...use a cast iron skillet. That is about the only way to achieve it. Many may make fun of cooking "skillet steak", but if you want that crispy exterior, the cast iron gives you the expanded surface area to do that. By using a skillet, ALL the meat is on the hot surface of the skillet. This also allows you to make some great sauces...especially with that butter!
Don......
I agree, you can never be too hot to sear a steak! Sealing in juices is another myth. That is impossible to do, especially on a grill. Searing is for flavor, as I explained above.
Now, the high end steak joints can come close to sealing in juices, but not totally. The Salamanders they use surround the meat with intense heat. What this method does is drive the juices away from the heat, which is on all sides, so they stay in the middle of the meat. Think about trying to seal anything from water...you would need something that is impervious and that will result in burnt meat.
That is why on the grill it is impossible. The grates get very hot, but the ambient temps are never hot enough alone to seal juices. Because the grates are alway hotter than the ambient air, those grates will drive those juices to the top of the meat. Hence the other myth....flip often!