Purchasing a rank will result in higher ranks to have a discount with the differences between the higher value rank and your current rank, so you will never overpay.

Villager ➞ Warrior Upgrade
2.99 USD
Buy
Warrior ➞ Hero Upgrade
9.99 USD
Buy
Hero ➞ Knight Upgrade
14.99 USD
Buy
Knight ➞ Baron Upgrade
19.99 USD
Buy
Baron ➞ Duke Upgrade
34.99 USD
Buy
Duke ➞ King Upgrade
64.99 USD
Buy