I love reading the graphs of camelcamelcamel. It's sometimes entirely obvious that two pricing algorithms are fighting for the buy box.

You can also see when an item is reaching its long term date[0]: 180-days(or 365 on some markets now) in inventory point: sudden drop in the price. The margin can get negative because the long term fee is very hefty.

Say you sell SD cards or a similar low volume, low cost item: at a certain point in time, the storage fees will be larger than profit, selling them for 0€01 then makes sense...

[0]https://sellercentral.amazon.com/gp/help/external/200684750?...