I don't think the price is the same if Euros are more expensive than US Dollars. For the Gold Edition, you're paying for the game and the season pass. The Libertad Pack is a pre-order bonus, so that means you can get Libertad Chorizo and Discos Locos with the Standard Edition. In the US store, the Gold Edition Steelbook are only available for consoles. If you buy the PC version, you're buying the game digitally and you won't get the steelbook. It looks like the Ultimate Edition is available for all platforms in the Europe store while it's only available on PC in the US store.
In some stores in the US, steelbooks are sometimes exclusive to specific retailers (GameStop, Best Buy, Target, etc.) and it would be given away to customers for free.
I don't know if the Ubisoft Store is set in stone, maybe in the future that could change once we are closer to the game's release.