The problem with cull cow burger is cull cow value + processing makes burger several dollars per pount higher than retail due to packers cost to slaughter and process a cow is much lower than what a butcher will charge to slaughter and process a cow.  We have been asked several times why we don't to a whole burger animal and everyone backs away when you tell them you need $8/lb for cull cow burger to break even.  Take a 1400# cow that hangs at 60% that is 840# hanging and will make approx 480# of burger.  840# @ 2.85/lb is $2400 for the cow as cull value so now figure 2400/480=5.  You have $5/lb in the burger before processing which will add another $2/lb since the processing charge goes up due to more grinding.  Now deal with pickup meat, put in freezer, run freezer, and take time to sell it and you will easily have another $1/lb in the burger.  In the end grinding a cull cow in todays market is far less favorable than selling them to the packer.  Run the numbers with a fat steer and you need to add another $1/lb to break even on freezer burger.  Paying 8-9/lb whne every where else is 6 or less becomes a hard sell when moving 10-20lb at a crack.