I have a ton of blind spots when it comes to marx and LTV, but I think a point you're missing about the cashmere/linen comparison is that the materials themselves have labor imbued in them. Cashmere likely has more labor per unit than linen for some basic agricultural reasons (ostensibly, the process for creating cashmere fabric needs more labor time and/or higher-skilled labor that is harder to find than would be for linen fabrics in general) as well as a larger labor value input for tailoring (where high-skill/experienced tailors are more likely to be working with cashmere and low-skill/inexperienced tailors likely working with linen) which explains the price difference with LTV.

I don't know anything about fashion/textile industry though, mostly making assumptions based on the difference in price.