Possible masterpiece bug

Iworb

I've got "Dark ritual" masterpiece. It says: "The first card in your hand gains full mana". When you cast this spell it gives you +30 mana (related to tips). BUT there's some cards with passive like: "Remove creature to opponents hand and it cost 300 more". Or "Sphinx's Tutelage" with ability "Whenever you draw a card, the first card in your opponent's hand costs 2 more" which could increase card cost more than 30.
So PROBABLY masterpiece card could act in wrong way. Who can confirm or reject that behaviour?