Remake Version: Upgrade Formula is extremely flawed

[XDConfirm]

The current formula for making the cost more expensive is very flawed currently.
Factors of the Formula are the cost of the upgrade, the amount of the upgrade that the player has, and the amount that the player is buying.

Demo Version of Cost Formula:

( Note: This exact code is not planned to be inside the game. )

// All of this is supposed to be inside a buyUpgrade() function
... {
 const amount = upgrade.amount;
 const cost = upgrade.cost;
 const buy = buy_btn.buy;

/* First Demo Method */
 function changeCostViaFormula() {
    let totalCost = buy * (cost + Math.floor(cost * ((amount * 10) / 100)));
    return totalCost;
 }

/* Second Demo Method */
 function changeCostViaFormulaForLoop() {
 let totalCost = 0;
 for (let i = 0; i <= buy; i++) {
    const iterate = Math.floor(cost + (cost * ((amount * 10) / 100)));
    totalCost += iterate;
 }
  return totalCost;
 }

// Examples
 const amount = 1;
 const cost = 100;
 const buy = 2;
 return console.debug(changeCostViaFormula()); // Returns a cost of 220
 return console.debug(changeCostViaFormulaForLoop()); // Should return a cost of 220

 const amount = 3;
 const cost = 450;
 const buy = 5;
 return console.debug(changeCostViaFormula()); // Returns a cost of 2925
 return console.debug(changeCostViaFormulaForLoop()); // Should return a cost of 2925
}