On a large scale actually and even for domestic individual usage, you can even buy diamond drills in your local tool store. They are also used in glass cutting, wire manufacture, abrasive materials, thermoconductive pastes and many elements of precise electronics and various (especially pressure) measuring tools.
This is 90% of things
other things have use-value, sentimental value doesn't depreciate, and they're overpriced anyway
there's no universe in which this is anything other than the whining of a (hopefully) dying industry
Interestingly diamonds are neat example of differences between value and price because they undoubtedly do have use value in real industry.
I think they're being used as tips in some industrial cutting machines because of their hardness
On a large scale actually and even for domestic individual usage, you can even buy diamond drills in your local tool store. They are also used in glass cutting, wire manufacture, abrasive materials, thermoconductive pastes and many elements of precise electronics and various (especially pressure) measuring tools.