If this idea is welcome and would come in-game I'd like to try the scripting.
It should be a good possibility to learn it since it shouldn't be too difficult.
So is it fine?
Also I suggest some changes about the prices and also about the bonuses of the amulets.
I think the luck bonuses, even though +4 LUK on the golden amulet is a huge bonus, seem reasonable, but the additional bonuses on magic attack are too much and should stay at +5 for all amulets.
I suggest taking Iron Ingots as the earlier in this thread mentioned metals.
Please take a look at below and yes, I think these amulets should be very expensive and a long-term target to get them

Four-Leaf Clover +

5 Iron Ingot + 50,000 GP =

Crozenite Four-Leaf Amulet

Crozenite Four-Leaf Amulet +

Four-Leaf Clover +

10 Iron Ingot + 100,000 GP =

Bromenal Four-Leaf Amulet

Bromenal Four-Leaf Amulet +

Four-Leaf Clover +

20 Iron Ingot + 250,000 GP =

Silver Four-Leaf Amulet

Silver Four-Leaf Amulet +

Four-Leaf Clover +

30 Iron Ingot + 500,000 GP =

Golden Four-Leaf Amulet
Before you search at the wiki:
1 Iron Ingot = 5 Iron Ores + 10 Coals + 1,000 GP

Four-Leaf Clover → Luck + 1, Magic attack + 5

Crozenite Four-Leaf Amulet → Luck + 1, Magic attack + 5

Bromenal Four-Leaf Amulet → Luck + 2, Magic attack + 5

Silver Four-Leaf Amulet → Luck + 3, Magic attack + 5

Golden Four-Leaf Amulet → Luck + 4, Magic attack + 5