when we take our(ok my parent's) cattle in for butcher, they use chuck roasts and other leftover roast pieces. it really depends on what steaks and roasts we want out of it first, then they grind leftovers for burger.
I pretty much do the same with wild game burger... use leftover 'roast' pieces and blend back in some pork or beef fat, depending on the game.
I guess it's a little different if you've gotta buy all the stuff at the store since they don't really have packages of 'leftovers'. Or maybe they do, might be worth an inquiry... heck, I get fish carcasses from the local (for free)... just gotta ask for it.