How to catch a vendor price increase before it costs you a year
Price creep rarely arrives as a letter. It arrives as a 4% bump on one line of a 40-line invoice. Here is the arithmetic that makes it visible, and the email that fixes it.
A vendor almost never announces an increase. What happens instead is that one line on a weekly invoice moves from $3.42 to $3.79, and nobody notices, because $0.37 does not look like anything. On 80 pounds a week it is $1,539 a year, from one line, on one item.
The three comparisons that matter
Comparing this week to last week produces noise — one delivery can be off for a dozen innocent reasons. Three comparisons separate signal from noise, and they answer different questions.
| Comparison | Threshold | What it tells you |
|---|---|---|
| Today vs 60-day median | More than 8% | A spike. Often a substitution, a short, or a market swing. |
| Today vs 90 days ago | More than 15% | A sustained increase. This one is structural and worth a call. |
| Today vs 12-month high | New high | You have never paid this much. Strongest negotiating position. |
Normalize before you compare
The most common way to miss an increase is to compare prices in different units. A case that quietly goes from 24 count to 20 count at the same case price is an 20% increase wearing a disguise. Convert everything to one base unit — price per pound, per fluid ounce, per each — before comparing anything.
Yield changes the real number
A 40 lb case of bone-in chicken that yields 26 lb of usable meat costs you a third more per usable pound than the invoice suggests. Compare on yielded cost or you will pick the wrong vendor confidently.
The email that works
Reps respond to specifics and ignore complaints. Give them the item code, the two dates, the two prices, and what the competing quote is. Ask one direct question and stop typing.
"Hi Dan — MT-2041 chicken thigh went from $3.42/lb on 12 Nov to $3.79/lb on 8 Jan, up 10.8%. I'm buying about 80 lb a week, so that's roughly $1,540 a year. Two other suppliers quoted the same spec at $3.45 this month. Can you get back to $3.50 or is there a spec change I should know about?"
That email works because every number in it is checkable. If your invoices are only in a shoebox, you cannot write it. That is the entire reason to capture invoices at all.