Valve have revealed update notes that include a nerf to Axe, the card that was the most powerful and the most expensive one on the roster. They offered a refund that may not cover the price some players paid, in some cases not even a half.
Players who bought Axe at the peak of the card's value may find themselves in a ditch, despite having this refund option. There were a total of 103 cards sold at the price of $38,73 during 28 November 2018, which is Artifact's launch day as well. The price quickly plummeted, but rose again to $27,77 on 30 November 2018, when 167 cards were sold at this price.
So, why is the card price important when the update is about game balance? Well, some players paid real-life currency for this card and then it got nerfed mere weeks later, from having 7/2/11 stats to 6/2/10. Due to the change in Artifact design philosophy, Valve decided to offer refunds for players who bought the card on Steam's marketplace.
The catch is that players will not be refunded the exact price they paid for the card, but rather the peak price within 24 hours of the announcement. This turned out to be $9,98 which is obviously way less than some players paid for it. In fact, this is less than the card cost at any point since Artifact's release until 19 December 2018.
At the time of writing, Axe's price was in free fall, standing at $6,59 with high chances of going even lower due to the nerf and potential players utilising the refund option. Keep in mind that those who bought the card after the announcement are not eligible for a refund.
It is worth noting that Valve originally intended not to have ongoing balance changes for Artifact's cards, but they have changed their approach, as stated in the above-linked announcement.
Valve also stated the refund option is a one time only and will not happen in the future, should other cards get nerfed. This sets an odd precedent, since players are now aware their cards' in-game usefulness may drop due to getting nerfed, on top of losing real-life currency value on the Steam Marketplace, directly influenced by a potential balance change. Needless to say, they will not get any refunds, should this happen.