I'm not familiar with the Board Game Arena price model - is it on a per games basis? I only found information for a premium subscription.
I'd guess that the prices increased either due to general inflation or that they're trying to match the price to the value of the physical products.
Excellent points. I was in middle school in the USA when the Gamecube released, and I remember there being a strong focus among my friends and myself about how powerful each console was and how they pushed graphics forward, especially with 3d models.
It seems that Nintendo wasn't focused on this aspect with the Gamecube, and their sales likely suffered because of it. But as you said, we can look back now and see that they had long-term vision instead of chasing the current craze.
It's interesting that Nintendo is in a similar boat with the Switch, but I feel that public perception of the importance of graphics has decreased so the Switch is able to thrive.