At the end of the day...the only person that you need to be satisfied with your bear is you.

18 lbs does sound a whole bunch light, though.

I killed a small boar a few years ago. It was around 140lbs. If I recall, I got a fair amount of meat off it, but didn't weigh it.

I do have to say that of all wild meat, bear meat is one of my LEAST favorites. Just don't care for it.