Grinding coffee is hard. It's very easy to get particles that are too fine, overextract, and ruin the taste. So some engineering is required to get a good result.

For these limited-run products, you're paying for the product development to a greater extent than you would for a product that sells in the millions. Software is very similar, someone could use Wordpress off the shelf, but they have a bunch of ideas for how their thing should be different, and so pay artisans $300 an hour to make their very own custom blog. The $1700 coffee grinder is the same effect at play.