Reducing specific titles' creation cost?

[Panoramic361]

TL;DR -- How can I set the piety & gold costs for a specific handful of titular titles to be lower than default? I want to encourage successful Lodbroking invaders to form these titular k_ titles instead of the dejure ones by making them cheaper. I want something more limited than KING_GOLD_CREATION_COST or TITULAR_TITLE_CREATION_COST_MULT

[I've been searching on the forums for a while fruitlessly, so apologies if this has already been answered. Thanks for any advice]

So I'm just getting into modding & I'm trying to make some personal tweaks to 867 England gameplay (well-trodden ground) and I'm starting with Halfdan/Ubbi/Bersi/other Norse invaders of feudal England. I want the invaders to create and hold onto new (titular) k_ titles that correspond to Northumbria/Jorvik, East Anglia, Mercia, and Wessex. I'm thinking that the invaders should only lay claim to the Anglosaxon kingdoms if they become closer to their subjects, so if they adopt Anglosaxon, Anglonorse/Englisc, or English cultures (I'm working off Erilaz's excellent NHO which tweaks the meltingpots).

I don't like the high costs of the Charlemagne-decision so I'm making new titular titles in a /common/landed_titles file and editing the existing dejure k_ titles to only allow certain cultures to form them -- I think I have a handle on title modding, but I'm not sure how to lower the gold and piety costs to incentivize their creation.

I see from this 2-yr-old thread that KING_GOLD_CREATION_COST and KING_PIETY_CREATION_COST in defines.lua are the variables to tinker with, but I don't want to change creation costs for all k_ titles. TITULAR_TITLE_CREATION_COST_MULT is also a factor, but again I don't want to lower costs for all titular titles. Is it even possible to define a specific creation cost for my new titular k_ title? Do I have to create a new variable in defines? Thx for any help/advice.

If anyone is interested in critiquing my code, this is what I have for a new titular East Anglian invader kingdom

Spoiler

k_east_anglia_norse_titular = {
        #color = { 60 109 121 } #taken from swmh_landed_titles.txt
        #color2 = { 255 255 255 } #taken from swmh_landed_titles.txt

        #cultural names taken from Erilaz's 00_NHO_landed_titles_England
        #TODO: should come up with a name to make it distinguishable from dejure k_east_anglia
        norse = "Austrængla"
        runedanish = "Østrængla"
        runeswedish = "Østrængla"
        runegothic = "Østrængla"
        danish = "Østængla"
        swedish = "Østængla"
        gothic = "Østrængla"
        norwegian = "Austrængla"
        gutnish = "Austraingla"
        icelandic = "Austrængla"

        #Should still need to hold relevant territory, so define capital
        #capital = 70           #Norfolk
        #culture = norse     #for randomly-created characters, esp. liberation revolts

        #Only allow Norse/middleScandinavian/Scandinavian rulers to create
        #might only allow pagans to form? or non-christians? idk
        allow = {
           AND = { c_norfolk = { owner_under_ROOT = yes } #Make sure actually own relevant territory!
                         c_suffolk = { owner_under_ROOT = yes }
            }
            NOT = { has_landed_title = k_england }
            OR = {     culture = norse       #Cultural restrictions to Norse invaders
                    culture = runedanish
                    culture = runeswedish
                    culture = runegothic
                    culture = danish
                    culture = swedish
                    culture = gothic
                    culture = norwegian
                    culture = gutnish
                    culture = icelandic 
            }
            #Lowered creation cost than normal to encourage duke-tier invaders to actually create it?
            prestige = 500 #prestige threshold for creation, not actual cost
            title_king_basic_allow = yes
        } #end allow

        # Creation Effect
        gain_effect = {
            prestige = 200
            wealth = 400 # crude way to recoup vanilla creation costs
            piety = 200  # crude way to recoup vanilla creation costs
        }
    } # end k_east_anglia_norse_titular