Two handmade rock wool sandwich panels can look identical on a quotation sheet yet quote 30–130% apart once flatness tolerance, core density, face gauge, edge closure and cleanroom fit-and-finish are unpacked. The spread is rarely pure margin: it hides in the precision of the manual lamination, the grade of the rock wool, the stiffness of the steel skin, the milling of the tongue-and-groove, and the sealing of the perimeter. This module disassembles the cost stack for overseas procurement engineers, pharmaceutical EPCs, cleanroom GCs and fire-safety subcontractors, then reassembles it into a process map for audit-grade handmade rock wool sandwich panel. SAMZOON, a Foshan source manufacturer, anchors the walkthrough with free pre-bid coupons, custom thickness, antibacterial coating options and South China cleanroom project QC.