If I'm using anything lower than about 90% lean ground beef, I will generally drain it before using it. I haven't measured it, but I suspect the meat I'm getting after draining a higher fat product is comparable to the 90% lean meat, but at a much lower net price per pound. Which tastes better? Hard to pick a winner.

I remember reading an article about testing on various grades of lean meat, for the most part they're fairly close to the stated percentage of fat, but there can be a variance of several percent. They probably prefer to err on the side of having less fat than claimed.

I did try weighing the raw meat, the finished meat and the fat drained off a couple of times, the meat and fat usually added up to about 95% of the raw weight, I assume the difference was a combination of what's left in the pan and any moisture or fat loss due to evaporation.

My wife read an article years ago about a way to remove even more of the fat from ground beef after cooking and draining it. You put it in a pan of boiling water for 10-15 seconds. I think pouring boiling water over it from a tea kettle has about the same effect. I believe this is how the 'loose meat' sandwiches at a place like Made-Rite are prepared.