Wine contains tannins, a natural substance incorporated into grape hides.
Suddenly though, you're paying a premium to be fashionable. Overall, this review of packaging cost for wine has these assumptions: a boutique winery with a run of 500 cases and not them owning the bottling equipment. https://objectstorage.ap-singapore-1.oraclecloud.com/p/0mmnTk-eCMSJ_TST0HoxLxdx-2PD1LzxKVxQpR3NNmmesS4z4yzh9-mPPAt9Xjeo/n/axqjqojndoew/b/Ruou-tay/o/Tiet-lo-nhung-bi-mat-san-xuat-ruou-Hennessy.docx.html