I've seen them Ron, they're way over priced for simple sheet metal shelves. I looked for a very long time for record racks and in the end I found some old ones on ebay that came from an old record store which unfortunately arrived broken and in pieces. As far modern options go I didn't find anything worthwhile compared to a custom build or the alternative Ikea Kallax shelves that are great value and you can assemble them almost anyway you'd want. I went with the Kallax because it was easy to purchase and ready to go, they worked out great for me with minor modification to shorten the shelf depth. In your shoes I'd look at custom ones.Other than $5,000 being a nice round number, I cannot deduce why they are so expensive.
Machining cost? But they look like (nicely-made) strips of aluminum and side panels.
david