Dry-aged steak costs far more before cooking. Where did much of the sellable beef go?

Answer: Evaporated and trimmed away

Evaporated and trimmed away ✓ — Right. Dry aging is partly a flavor upgrade and partly a yield sacrifice: water leaves the exposed meat, then the dark, dried crust has to be cut off. A Texas A&M dry-aging report shows dry-aged shortloins falling from about 76.5% retail yield at 14 days to 69.8% at 35 days, while wet-aged ones stayed near 86-88%. The surprise is that the premium is not just for time; some of the product literally disappears before sale.

Locked inside muscle fibers — Not quite. Muscle fibers do change during aging, but they are not hiding the missing mass. The big economic difference is visible: evaporation reduces weight and trimming removes the dried surface. Wet-aged beef tenderizes in a sealed bag too, yet it avoids most shrink and crust loss, which is why the same biological aging can be much cheaper.

Melted into surface fat — Almost the opposite. Fat helps protect and lubricate a steak, but it does not absorb the missing lean meat like a sponge. The sellable loss comes from water leaving the lean surface and from cutting away the crust. That is why dry aging usually starts with large, well-marbled cuts: small steaks would sacrifice too much of themselves.