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.
I prefer the aesthetic of vertical. There's just something about it that makes it look like a "proper" collection to me. Of course one downside is that it'll definitely mess up the components if they aren't in baggies or some type of organizer.