Joining the Amazon Selling Partner 360 programme will cost you €1600/month + 0.3% of your total sales in the previous calendar month, including the item price, excluding returns, fulfilment, gift wrap or other charges ("Total Monthly Revenue") + taxes. The total monthly costs are max. €5000.
Here is an example: Between 1 July and 31 July 2020, Kristin's jewellery business, a hypothetical seller on Amazon participating in the growth programme, made €130,000 of total monthly revenue across the EU (+ UK [no longer part of the EU as of 01/01/2021]). Kristin's jewellery shop would be charged €1990 (+ tax) on 1 August. Calculation: (€1600 + (0.003*€130,000))
Please note that the calculated costs are based on your total EU-wide (+UK [no longer part of the EU as of 01/01/2021]) monthly revenue of the previous month ("total monthly revenue" = item price* quantity; total monthly revenue does not include returns, fulfilment, gift wrap or other fees) and therefore can vary month to month.