Terraria – How to farm key molds

What I did was to build an artificial meteor biome using 50 blocks of meteor ore inside the underground corruption and hallow. By the time you have reached hard mode you should be able to one hit kill the meteor heads. Within 10 minutes in each biome I was able to get all the light/dark souls I'd need to make every end game item. I've not yet tried using statues and a lava film to farm souls, but considering that spawned mobs don't drop cash I suspect it possibly won't work. However, a corrupt bunny/fish spawner placed inside of the underground hallow/corruption should work just fine, netting you both the massive cash and a ton of souls.

Enemies spawned from statues cannot drop a dungeon key.

Below is the code that spawns the key drop as you kill an enemy in a biome (the only code that spawns a dungeon key in the game). As you can see, the chance is one in 4000. (On average, every 4000th enemy drops a key.)

I changed the random number to be a confirmed key drop instead, and built a contraption with statues to spawn enemies in an ice biome. I killed a few normally spawned enemies in the biome and all of them dropped a key. Then I spawned a few enemies from the statues and none of them dropped a key.

if (Main.hardMode && this.value > 0f)
{
    if (Main.rand.Next(4000) == 0 && Main.player[(int)Player.FindClosest(this.position, this.width, this.height)].zoneJungle)
    {
        Item.NewItem((int)this.position.X, (int)this.position.Y, this.width, this.height, 1533, 1, false, 0, false);
    }
    if (Main.rand.Next(4000) == 0 && Main.player[(int)Player.FindClosest(this.position, this.width, this.height)].zoneEvil)
    {
        Item.NewItem((int)this.position.X, (int)this.position.Y, this.width, this.height, 1534, 1, false, 0, false);
    }
    if (Main.rand.Next(4000) == 0 && Main.player[(int)Player.FindClosest(this.position, this.width, this.height)].zoneBlood)
    {
        Item.NewItem((int)this.position.X, (int)this.position.Y, this.width, this.height, 1535, 1, false, 0, false);
    }
    if (Main.rand.Next(4000) == 0 && Main.player[(int)Player.FindClosest(this.position, this.width, this.height)].zoneHoly)
    {
        Item.NewItem((int)this.position.X, (int)this.position.Y, this.width, this.height, 1536, 1, false, 0, false);
    }
    if (Main.rand.Next(4000) == 0 && Main.player[(int)Player.FindClosest(this.position, this.width, this.height)].zoneSnow)
    {
        Item.NewItem((int)this.position.X, (int)this.position.Y, this.width, this.height, 1537, 1, false, 0, false);
    }
}