Student reported that the voucher that was given to them gives 25 USD discount but Github Tshirts are worth 30 USD now, after discount, it asks to pay 15 USD for shipping and tshirt.
Sorry for the inconvenience. Please contact GitHub Education support for assistance.
A note for students and educators in the European Union: Since July 1st, 2021 every item imported into the EU from non-EU countries is subject to import turnover tax (previously items worth less than 22 EUR were free). So ordering a t-shirt from the GitHub store with a voucher costs approximately 7 EUR. Since only one coupon can be applied to an order, getting multiple shirts with multiple codes will result in paying import turnover tax for every item.