(Posted on the GOG forum early this morning but haven't got a response yet, so I'm posting here, too.)
Why isn't the Gold Bundle available on GOG?
For the game and all DLCs, it costs $109.89 on GOG vs. $60.39 on Steam.
Steam users pay $50 less than GOG users for the same content, and if they own all previously released content, get a 45% discount on each new DLC:
"If you already own some of the products contained in the bundle, purchasing the bundle will allow you to "complete the set", paying only for the products you don't already own while still receiving the full bundle discount on each of those products."
GOG's catalog works somewhat differently from Steam, but this shouldn't be a problem: GOG could implement the Gold Bundle as either a series discount or a permanent sale rather than a bundle product in the catalog. New DLC could then be added to the series discount or sale page as they are released (instead of creating a new bundle product each time).
This needs to happen ASAP. A small upcharge for DRM-free isn't unheard of, but the current situation is ridiculous.
Edit: The bundle is even cheaper ($44.50) this weekend because of the Stardock sale.