It also happens in online marketplaces like Amazon but luckily there are tools to track price changes like https://camelcamelcamel.com/ (disclaimer: not affiliated at all, just a happy user). Wish there were more tools like that but for retail.
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?...