BOM Cost Roll-Up & Margin Checker: Catch Negative Margins Before You Quote Them

The problem this kills

You quote a product at a price that made money last year. But copper went up, your contract resin supplier raised prices twice, a subassembly got re-sourced, and labor rates ticked up — and nobody re-rolled the cost. The number you're quoting against is stale, and on some SKUs your "margin" is now negative. You're selling at a loss and you won't find out until the quarter closes.

The real cost of a manufactured item isn't a single price — it's a tree. The finished good is built from subassemblies, each subassembly from components, each component with its own price and the quantity you consume. To get the true cost you have to roll material up from the bottom of the bill of materials, level by level, then add the labor and overhead of each operation. Most teams do this in a heroic spreadsheet with nested lookups that one cost accountant maintains. It breaks silently when a price list changes, when a component appears at two levels, or when someone uses an expired price because the latest one wasn't pasted in.

When the cost is wrong, every quote built on it is wrong. This tool makes the roll-up a real, governed calculation — and it tells you, loudly, the moment any item's cost has crept above its price.

What you'll build

A simple internal web app for your costing team. You import your multi-level BOM (parent SKU, component SKU, quantity per, and the operation if you track labor) and a component price list with effective dates. You optionally import labor rates and standard times per operation.

The tool walks the BOM from the bottom up: it prices each leaf component using the latest effective price as of your costing date, multiplies by the quantity consumed, sums the components into each subassembly's material cost, then rolls those subassemblies up into their parents — level by level — until it has a true material cost for the finished good. It adds labor and overhead per operation if you provided them. Then it compares the rolled cost to each item's sell price and flags every thin or negative margin. The cost accountant reviews the roll-up and the margin-alert list, fixes what looks wrong, and approves before any standard cost is published or exported back to the ERP. Missing or expired prices are never silently treated as zero — they're surfaced and flagged.

What's inside the Implementation Plan

The downloadable plan is a step-by-step file you paste into an AI coding agent. It opens by interviewing you about your business — how deep your BOMs go, the exact column names in your BOM and price-list exports, how you identify a SKU, how you pick which price is "current," whether you cost labor and overhead and how, what margin threshold counts as "thin," and the messy exceptions (phantom assemblies, by-products, scrap factors, components that appear at two levels, units of measure that don't match). It reflects a short tailored spec back to you and gets your thumbs-up before it builds anything, so the roll-up matches how your products are actually built and costed — not a generic template.

From there it walks the agent through the data model, the BOM and price-list import with duplicate guards, the bottom-up roll-up engine, the labor/overhead layer, the margin comparison and flagging, the cost-accountant approval gate, and the standard-cost CSV export. Every step ends with a ready-to-copy prompt. There's a full "No API yet?" path that uses Google Sheet / CSV imports as the data source and produces a clean standard-cost CSV in your ERP's exact columns — so you can build and run the whole thing this weekend regardless of what ERP you're on.

The governance it includes (this is the point)

A standard cost feeds your quotes, your inventory valuation, and your margins — so the controls aren't optional. The plan builds in login so only your costing team can use the tool, row-level security so you only ever see your own organization's BOMs and prices, a complete audit trail of who changed which cost assumption and who approved which roll-up, a hard human-approval gate so no standard cost is published to the ERP until the cost accountant signs off on the rolled numbers and the margin alerts, and duplicate guards so the same BOM line or price record can't be counted twice when you re-import.

Who it's for

Cost accountants, manufacturing and process engineers, and product or operations managers who quote work and protect margin. If you can explain how your products are built — what goes into what, and how you decide which price is current — you can build this, and you'll stop quoting against costs that quietly went underwater.

You've got this — start with the plan, paste the first prompt, and answer the interview. You'll have your first true rolled-up cost and margin-alert list on screen before the weekend's out.