Amazon repricing for wholesale and arbitrage sellers
For sellers who buy stock and resell it. Marginary picks the price that earns the most per day after Amazon's fees, raises it when your stock is running out, and writes down why every time. Switch on the comparison group and it leaves a slice of your catalogue alone, so the dashboard can show whether it is actually making you more money.
Cut the price from $24.99 to $23.45 after the best rival offer undercut you to $23.40 from $24.10, 12 minutes ago. Matching the lowest offer is modelled to earn $0.62 less per day. Featured Offer odds go from 41% to 68%.
Held at $18.99 instead of moving to $17.80 because a safety rule stopped the move. Your minimum price of $18.99 stopped it going lower.
Raised the price from $31.00 to $32.40 because expected daily profit peaks there. These odds still lean on the general model, with only 4 recorded observations on this listing.
Every check writes one of these, including the ones where nothing moved. Sentences above are illustrative — the structure is the product's, the figures are samples.
What you actually get
Nine things it does, and one thing it will never do: move a price without leaving you a reason you can read.
Undercutting maximises your chance of a sale, not your money. Marginary estimates how much of the day you would hold the Featured Offer at each price in your range, how many units that moves, and what each one earns after fees. Then it picks the peak.
Sometimes that is a cent above the cheapest offer. Sometimes it is a dollar above, with a smaller share of the Buy Box and more money at the end of the day. The sentence tells you which.
Illustrative curve. The real one is fitted per listing from that listing's own recorded history.
Marginary reads your FBA stock every hour and works out how many days it will last at the pace you are selling. When you are going to run out, it prices up rather than selling next week's units cheap today. When you are holding far more than you will sell in the next few months, it prices down to move it.
Most repricers would call 87% Buy Box on those nine units a win. It is a stockout with a trophy.
Raised the price from $31.00 to $32.90 because your rule "Running out before restock" matched. Featured Offer odds go from 71% to 54%.
Illustrative figures. Stock is read from Amazon's own warehouse count, not from what the listing claims.
Any repricer can show you a profit number after a month. What it cannot show you is what those same items would have earned if nobody had touched them. Marginary keeps up to a quarter of your catalogue untouched, chosen by a fixed rule nobody can game, and measures both groups side by side.
The dashboard shows profit per item per day for each group, the difference, and the range it is confident in. Until there are enough items and enough days on both sides, it says so next to the number rather than calling it proven.
Somewhere between +$0.22 and +$1.19. Illustrative figures. The comparison is not called proven until each group has at least five items and fourteen days of selling behind it.
"72% Featured Offer" tells you what a model believes. It doesn't tell you why your price moved.
Marginary writes one plain sentence per decision — what it did, what the competition did to cause it, what that beat, what stopped it going further — assembled from what the cycle already worked out and stored. A decision from last Tuesday reads exactly as it read on Tuesday.
Rule #4 fired. Price updated.
Cut the price from $24.99 to $23.45 after the best rival offer undercut you to $23.40, 12 minutes ago. Matching the lowest offer is modelled to earn $0.62 less per day.
A brand-new listing has no history, so its odds are the general model wearing a percentage sign. Marginary says so — in the sentence — until that listing has enough of its own measured observations to speak for itself.
As this listing records its own behaviour, the bar fills and the general model steps back. The sentence changes with it.
Seven days per rule: how often it fired, what it did to your Featured Offer share, and what it was worth per day — labelled as modelled, because it is.
A rule that fires constantly and improves nothing is a rule you should delete, and you shouldn't have to read a log to find it.
Fires most, changes least. Worth deleting.
Holds are recorded with the same care as changes. Your floor, your per-change cap, your daily and hourly limits, the price-war brake — whichever one bit gets named.
A repricer that silently does nothing looks identical to a repricer that's broken, right up until you check your sales.
Held at $18.99 instead of moving to $17.80 because your minimum price stopped it going lower.
Held at $42.50 because prices on this listing have fallen four times in an hour. Marginary stopped following them down.
Held at $11.25 because this item has already changed price 3 times today, which is the limit you set.
You think in "never below 15% return", not "never below $18.43". Marginary takes what you paid plus inbound shipping and other costs, runs the full Amazon stack — tiered referral rates, FBA fees by size tier and weight band, storage, the tax Amazon adds to its own fees in Canada — and inverts it.
An item with no cost basis is never priced at all. That's checked before every single decision, not once at import.
Change a cost and the floor moves with it, instead of going stale.
Ask what a price would do before you set it. Any candidate price runs through the same fee model, odds and demand curve the live engine uses, so the preview and the engine can never disagree.
Replay a strategy against a listing's own recorded market history to see what it would have decided. It's honest about its limit: it can tell you what these rules would have chosen in those conditions, not how competitors would have reacted.
Change a cost, a stock level or a fulfilment method and the whole ladder recalculates. Nothing is written.
Objection, handled
Two of these cannot be switched off. The rest are yours to set, and they apply to everything — your own rules, our decisions, and manual changes alike.
Not by a rule, not by the optimiser, not by accident. You set a lowest and a highest price per item, and nothing crosses either.
A listing pulled from Amazon knows what it sells for and nothing about what you paid. Without a real floor it sits blocked, with a line telling you what's missing.
As a percentage, a dollar amount, or both. The smaller one wins.
So your listing doesn't look unstable to buyers.
One cap on everything, so nothing runs away.
Pointless one-cent moves get skipped.
Round to .99, .95 or .00. Always down, never up.
When prices on a listing keep falling fast, Marginary stops following them down.
Amazon usually wins on price. Sitting still beats losing money.
One button freezes every price where it is. Marginary keeps recording what it would have done, so you lose nothing by using it.
Checked before every single decision, not once at import. Nothing you have not finished setting up can be moved by anything — not a rule you wrote, not the optimiser, not a manual change.
Getting started
You grant permission to read your prices and, later, to change them.
Pull your catalogue straight from Amazon, upload a CSV, or paste one in. Imported items arrive paused. Run the pull twice and it updates rather than duplicating.
What you paid, shipping in, anything else. This is what makes the floor mean something.
Start with Profit maximiser. It optimises inside your range, backs off when Amazon holds the Featured Offer, holds in a price war, and raises prices when you're running low on stock. After that it runs on its own, as often as you choose — every five minutes through to once a day.
Pricing
A plan is one number — how many items Marginary prices for you at once. Paused and archived items cost nothing.
Every plan is the whole engine — you are buying capacity, not capability. Starter's first fourteen days are free. Full pricing details
Before you ask
Marginary runs every check against your real catalogue and writes down every decision and the reason for it. Nothing moves until an item has a cost and a floor, one button freezes the lot, and the comparison group tells you whether it earned its keep.
14 days free on Starter · emergency stop from day one
