EFN Fees: How much more than RM Click & Drop?

I am just looking into using EFN for some of my listings in Europe but trying to find out what the additional cost will be is proving difficult.

At the moment, I am using Royal Mail Click and Drop to fulfil our orders in Europe using the IOSS system; here in the UK I do use FBA, so creating EFN listings isn’t an issue but I want to know, naturally, how much more expensive this will be so I can adjust my asking prices accordingly.

At the moment it is costing around £6.00 to post a 100g package with a pair of sunglasses in it, to a European customer. Do you think Amazon’s EFN fee will be more that this and, if so, approximately how much?

Many thanks to anyone who can help.