The cheapest listing and the cheapest purchase are not the same thing
A discount is only a discount once shipping and import fees have been added to it. We add them, keep the record, and tell you when the total reaches the number you named.
A discount you can verify
Amazon shows you a percentage off. It does not show you what the item will cost delivered to where you live. Those are different numbers, and only one of them leaves your account.
Every price we record is split into base price, shipping and import fees, then added up. The total is what we compare, chart and alert on. A listing with a large discount and heavy fees can lose to a plain listing with cheap delivery, and you can read that line by line.
The split matters when you are deciding quickly. A small drop in the base price means nothing if the shipping fee moved the other way at the same time. The total tells you in one glance which of the two happened.
Name your number instead of watching
A price alert is a condition you write down once. The plainest one is also the most useful: tell me when the total reaches this amount or drops below it. Set it at the price you would actually pay, then close the tab.
You can also work in percentages, measured against the last recorded value. Or you can set a target amount on one component instead of the total, so a change in shipping alone can reach you. Conditions combine with AND and OR, so "under my number and in stock" is one alert rather than two.
Alerts are quiet by default. A cooldown holds the next message for sixty minutes unless you change it, and the clock runs separately for each tracked product, so one restless listing cannot bury the rest.
Back in stock is the better signal
The deal most people miss is not a price cut. It is a product that was sold out reappearing at its usual price, before the listing gets picked over again.
Availability conditions fire in both directions. One tells you when something sells out, which is worth knowing if you were hesitating. The other tells you when it comes back, and that is the one that saves money.
The record survives the gap. If a price goes from one figure, through a stretch of unavailability, to a lower figure, that is recorded as a price change rather than lost in the blank in between.
How much history sits behind the number
Recorded checks are kept, so the lowest, the highest and the average you read are drawn from the record for that product in that country, along with the day each extreme happened and how long it has been under observation.
Those three figures are computed only over checks where the product was available and had a price. Stretches where nothing could be read do not drag the average down and make an ordinary price look like an offer.
The record has gaps, and we would rather say so. Amazon blocks automated checks sometimes, some listings hide the price, and some are not purchasable from a given destination. A blocked check is stored as a check with no number, with the reason it failed, and each country's record also carries the share of checks that found the product available.
What it covers, and what a credit buys
Coverage is three marketplaces: Bolivia, Peru and the United States. That is the entire list. Other countries exist in the system and are switched off, and if you try to track one the request is refused before any credit is touched.
One credit puts one product under tracking in one marketplace for thirty days. The same product in a second country is a second credit, because it is a second price someone has to go and read. Credits are not returned if you stop early.
A new account starts with credits already in it, granted outright rather than counted down. Product pages here are public, so you can read a price and its history before deciding whether any of this is for you.