If it hadn't used mother of pearl and tortoiseshell, which weren't particularly rare at the time, they would have used things like rosewood, ebony, and ivory. So either way, precious materials were going to be used.

At least they are being used in the service of Art, and Music, instead of something vain, or selfish, like jewelry or beauty accessories. If these materials are going to be harvested anyway, using them to create a fine musical instrument, which can then be used to create beautiful music for a century, or possibly longer, is a worthy use of those precious natural materials.