General contractors manage more supplier accounts, more commodity categories, and more invoice volume than any other trade. When commodity prices move, supplier invoices do not always follow. The difference accumulates across every project.
A two-person residential GC and a billion-dollar commercial firm are both general contractors. The difference in invoice volume is orders of magnitude. The invoice exposure problem exists across both.
Volume accounts and negotiated tiers are real. They are also set once, reviewed rarely, and calculated against base prices that move every month.
General contractors with established account relationships at major distributors do receive below-list pricing. A high-volume account at Ferguson, White Cap, or Fastenal negotiates a discount tier — typically based on annual purchase volume and product category — and that tier is applied to every invoice until the next contract review.
The discount percentage stays the same. The base price it is applied against does not. When the commodity underlying a product category moves 8% in either direction, the invoice price is not automatically adjusted. The discount is calculated off whatever base the distributor is using that month. The Ledger compares what the invoice actually charged against what the market data says the price should have been — not against list price.
A plumber tracks copper. An electrician tracks copper and conduit. A general contractor tracks all of it simultaneously across every subcontract and direct purchase.
| Commodity | BLS / FRED Series | GC Exposure | How Overcharges Occur |
|---|---|---|---|
| Structural Steel | PCU33231233231212 | Framing, structural components, rebar, beams on commercial and civil projects | Steel prices dropped in late 2024 before rising 3.8% YoY in Aug 2025. Invoice prices at distributors do not always reflect downward moves when they occur. |
| Framing Lumber | WPU081 | Wood-frame residential and light commercial construction — one of the largest single material cost categories | Lumber is among the most volatile construction commodities. A budget locked at 2023 prices and a project breaking ground in 2025 requires an explicit escalation review — which rarely happens on supplier invoices. |
| Copper | WPU10260314 | Electrical rough-in, plumbing, HVAC — either directly purchased or embedded in subcontractor bids | Copper-based building materials were at least 10% higher in late 2025 than a year earlier per Statista/BLS data. GC invoices for copper-containing products do not always reflect commodity timing. |
| Diesel Fuel | WPU057303 | Embedded in fuel surcharges across all material deliveries and equipment operation | Fuel surcharges are billed as a percentage or flat fee. When diesel prices fall, surcharges are not automatically reduced. They persist until the GC disputes them or renegotiates. |
| Concrete / Cement | PCU32731-32731 | Foundations, flatwork, structural pours on commercial and civil projects | Concrete block pricing has been relatively stable, but ready-mix and specialty mixes carry regional variation that does not always correspond to what appears on the ready-mix distributor's invoice. |
| Aluminum | WPU101 | Storefront, curtainwall, windows, roofing trim, mechanical equipment housing | Tariffs pushed aluminum effective rates to multi-decade highs in 2025. GC invoices for aluminum-containing products absorbed those increases — but base price reductions, when they occur, are slower to appear. |
| Construction Materials Index | WPUSI012011 | Composite index across all construction inputs — useful as a baseline benchmark | The overall construction materials PPI rose 2.9% from Jan–Dec 2025 per AGC/BLS analysis. That index is available monthly. Supplier invoice pricing is not always recalibrated at the same frequency. |
Each pattern is a mechanism, not an accusation. Distributors operate complex pricing systems. These are the points where the system produces errors that favor the supplier.
The Ledger does not produce estimates. It produces documentation — date, line item, amount invoiced, verifiable market rate at the time of billing, and the delta between them.
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