For my Amazon FBM Sellers:

In the last 60 days we have seen a massive uptick in Amazon adding shipping charges after shipment.

Some of these items we have sold before paying $24 a label are now being upcharged to $50 a label.

Started in August and continues into October.

All shipping purchased through seller central, is adding 7% to the total label costs this year.

Opening tickets now, but to check this yourself:

https://sellercentral.amazon.com/manage/finance/transactions

Then look for "Chargeback due to under charging postage label purchased"

You can also grab your entire year report and send it to your LLM of choice to see the full damage.