I was wondering the same thing this past weekend.
I smoked a 7.5# pork shoulder on Saturday.
As I was preparing it for the brine, I noticed that it had a pretty decent layer of fat on top of it. As I decided to trim that layer of fat off, I noticed that it was not fat, but rather skin. I did not notice this at the store when I purchased it.
Two days later, after the prep, I smoked the shoulder for nine hours, until it was at an internal temp of 215.
I pulled it out of the smoker and let it rest for about 30 minutes before I pulled it apart and everyone devoured it.
While I was pulling it, I noticed that there were two large bones in the middle of it, which made me think about the overall meat poundage even more.
So, if the packaging said that it was a 7.5 pound pork shoulder, but I removed an outside layer of thick skin and then the two large bones in the middle, what was the overall total of meat that was consumable? Maybe 5 pounds?
Wow, sounds like a wordy math problem from back in the days in school ...