While the deck itself is free, AnkiHub costs money. AnkiHub has multiple full and part-time software developers dedicated to improving and maintaining the software in addition to regularly adding new features.
Please consider the average price of a textbook and how much content is in this deck. We pay multiple people and have 100+ volunteers that help update and maintain the deck.
While we initially relied on donations to help fund the deck updates, it is a much larger project now and donations aren’t able to cover the costs associated.