In the Checkout process , you will be asked to key in your postcode and state to determine a freight charge.
This Shipping costs will not show up on your order summary.
Shopify needs to know the customer's billing/shipping address before it calculates the relevant tax and shipping rates. The shipping address and freight charge gets added on the second page of the checkout process.
With PayPal Express, customers are first taken to the PayPal page where they input their credit card information. Once PayPal gets a billing address, they send that to Shopify in order for us to calculate which shipping rates and taxes are applicable.