My family likes these so I pay attention to sales. This is based on my own experience.
All baby back ribs. at least to me, are not alike, just like a pound of bacon is not all alike. It's difficult to describe. In my limited experience less expensive ribs have less meat. They look scrawny.
A couple of years ago I found some on sale fo $2.99/lb. They didn't look quite good. In the same store I found some for $5.99/lb that looked much nicer. I asked someone from the meat department to explain the pricing. His only explanation is that they came from different suppliers.
Perhaps someone will come along that has an explanation. To me, just like bacon, I've learned to have preferences.