OK, What can i change to decrease the cost?
The entire tile idea is a bit of a mess in my professional opinion. If your goal is to help the Jotun Oligarchy, then here are some ideas.
If you want to provide the Jotun Oligarchy with food without making it easy for other civilizations to get to, you can make some fruit bearing trees that grow fruit about 12 feet above ground level. A giant can reach up and grab it, but a normal person would need to jump or climb.
If you want to give a blessing to the Jotun Oligarchy and not others, you can change their home tile. This will be difficult for other civilizations to interact because its already giant infested so you don't need additional monsters.
If you want to harm other civilizations, you can replace tiles near them with less useful tiles. For example, if a civilizations trait is sailing you can remove the water tiles near them and replace them with say... Mountains or something.
An alternative way to harm one civilization and not others is to consider their differences. Instead of complex demons, ordinary animals can suffice. Solitary predators tend to avoid dangerous prey if they can so they would be less inclined to attack the Jotun Oligarchy. A similar idea would be to put piranhas in the water to make sailing more dangerous as the Potato Pirates would take to the waters much earlier than the Jotun Oligarchy.
... I should play as a god in the next Gridhood game that pops up.