I grew up in the meat business and have probably cut up about 10,000 deer.
Anywhere from 30-50% is about right. Depends on the shot. Depends on how much fat is on the deer.
A hit in the shoulder will take out some good meat as it will be all bloody and nasty.
A gut shot will usually ruin the tenderloins
It also depends on whether the butcher is doing it all boneless or just cutting it up on a saw. Bones weigh a lot!
You get the point.

You will normally get more meat from a bow kill than a gun kill due to the lower "shock" of the arrow vs a slug or bullet.