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Multiple addresses
Multiple addresses , especially internationally, seems seem to be difficult for many of these businesses, especially with international orders. Ethical Swag, for example, ships to multiple addresses only if less than 20% are international shipments.
Eco-friendliness
Most company's use similar suppliers and so the maker of the t-shirt seems to typically have has their own Environment & Sustainability goals(ESG) or Corporate Social Responsibility(CSR) goals. So if If this is considered an important consideration than we can prioritise products/manufacturers that have ESG -- or resellers that have good CSR – or both.
Price
The estimates above are highly dependent on what is needed, tax rates, and shipping take it address. Take the estimations above with a big lump of salt. Generally speaking what you can see in the table above is:
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