Best way to calculate fulfilment costs for Amazon?

[Callum9]

Hi,

I'm starting my first brand selling supplements and I'm currently looking at fulfilment options. I've found that Amazon fulfils orders from other sales channels and I was wondering if there was any extra costs rather than customers going through Amazon to purchase? I'm ordering 10,000 units of the same supplement, £0.50 per unit and was going to retail at £9.99 + shipping. Dimensions of box are 9.5 x 5.5 x 2.75cm and weighs 20 grams.

All help is appreciated, thanks!