Difference between Printful and Shopify shipping

[soapbox-tshirts]

Morning.

I'm in the process of setting up our online store, and I want to offer free shipping for customers in Europe and the USA.

I've set up the pricing of the retail product to reflect that, and have worked out all the VAT and sales tax implications etc etc.

Whilst in the process of doing this, I noticed that there is a difference in the price of the European flat rate that Printful charges me to what Shopify put on the cart to the customer.

For example, an 11oz enamel mug will cost £3.15 European flat rate to me (as charged by Printful), but on the Shopify checkout to my customers, is quoted as £4.06. A £0.91 difference.

What's going on here?

The customers on my Shopify site would pay retail price, which includes free shipping.

I get charged the product, printing, fulfilment, £3.15 shipping and tax by Printful.

Am I missing out on anything here?

Why do Shopify and Printful charge different European flat rate costs?

Obviously, I need to work out an exact cost of the producta and shipping, as that will be reflected in the sales tax/VAT price which I need to account for in the books.

Any thoughts?

Thanks,

Nick