I always wonder about this when buying my tri-tips from Cash$Carry. Last cryovac weighed in at 16.2lbs for 5 of them and after trimming and packaging I was left with 13lb 9oz of roasts. I take most of fatcap off. That's about 83%.
Of course, you're results may vary.
Pete-my first UDS,a brick pizza WFO, a leaky Chargriller offest, wifes Weber Genesis gasser,a Lightening Fast RED Thermapen, new baby Traeger