@mei in PKP IC you can sometimes get a ticket from Warsaw to Berlin (via Poznań) cheaper than to Poznań. I think at least in part because international travels are taxed VAT 0% but domestic are at VAT 23%
@IngaLovinde@mei ok I just got it first try, even if the difference is just pennies: week ahead, ticket to Berlin is discounted by Super Promo International, VAT 0%, but to Poznań it's regular price + VAT 23%. To not make it easier, currency rates seem to be a variable in this . Still, simpler and much cheaper way is to ride IC and not EIC.