LVDTs are fun! I bought one for a project a few years ago (since abandoned), and have been slowly designing my own readout electronics for them. Three revisions later, and the performance is very good - to the point that I've bought more increasingly precise measurement gear to benchmark how it's performing. Currently, I'm testing it against some good glass scale linear encoders, and a capacitive gauge with a single-digit nm noise floor.
So many don't buy an LVDT, I guess.