The cheap stuff is. If you get the avocado mayo, it generally comes in a glass jar and is about the size of the OP.

For most things where dropping it is likely and would definitely break it. It also lines up with the cost change for glass going up as the container gets bigger.

I figure part of it is people having a preference for the lighter jar for big quantities, and liking the rigidity of glass for the smaller ones.

90%

Nearly. The exceptions would be for pasta sauce, pickled or fermented things. An even some of those are plastic.