$ Furnace Levels 1.4.6

"Main Settings": {
"Currency Type": "Economics", ⇚ Economics / ServerRewards / Item
"Currency Item ID": 0,
"Currency Display Name": "$"
"Currency Item ID (only if type is Item)": 0,
"Large Furnace Cost Multiplier - Default 1.0x": 1.0 ⇚ Option to increase cost of upgrades for large furnace.

},

"Speed (Default is 0.5 - Lowering value increases smelting speed)": {
"Modifier": [
0.5, ⇚ starting modifier, Level 1
0.4, ⇚ Level 2
0.3, ⇚ Level 3
0.2 ⇚ Level 4
],
"Upgrade Price": [
0, ⇚ first value is only for index purpose as Level 1 is starting level.
30, ⇚ upgrade price for Level 2
50, ⇚ upgrade price for Level 3
70 ⇚ upgrade price for Level 4
//ps. you can create as much levels as you want, just add more values.
]
}