I believe the cost of diamonds that you can purchase via the Kafra shop needs to be lowered to reflect the in-game value of zeny at current or approximate inflation levels.
For instance, current conversion rates when selling Kafra Points are 1:5000, sometimes higher. So that means 1000 Kafra Points would equal 5,000,000 zeny in game. Meaning 5 million zeny is worth $10 give or take current inflation levels. Diamond services from 10k diamonds up to 20k diamonds sell from 1 million zeny to 2 million zeny.
Currently, 20k diamonds bought through the Kafra Store costs $30, so you can see the discrepancy between the values in-game, where it's far cheaper to pay for services in the game or obtain the diamonds through questing yourself. The cost of the Kafra Shop diamonds far exceeds their convenience.
I would suggest a pricing model that puts the 20k diamond package around $5 for increasing the convenience factor and likely sales.
Edited by flukeSG2, 20 September 2018 - 02:07 AM.