I have no idea if I can compare them this much but why does SpaceInvasion get this for 2500 bits:
Quote1x build field on all planets
All planets will be expanded by one build field, this applies to all planets of the connected SpaceInvasion Accounts. If a planet is deleted, the build field will also be forfeited.
And damoria gets this for only ONE castle for 5000 bits. Isn't that a bit expensive?
Quote1x field for secondary castle
Connected Damoria Accounts will receive an extension of 1 build field, which can be used in the shop for the selected secondary castle.