A lot of these items (likely all) created by Spiber would be considered novelty items. If I remember correctly, didn't Spibers denim piece have only 4% Brewed protein vs 96% cotton?
Here is a link to their $950 denim pants. You could also grab their $1000 denim jacket. All with 4% brewed protein...
And just for reference, here is a link to the only other denim pants on the Goldwin website. They cost $300. So the mark-up for Spiber's 4% "brewed protein" was $650 more than the regular denim. Does that really sound like an economical product?