

With all these options on the table, we can immediately rule out directly purchasing all 24 cosmetic items with Apex Coins. This is definitely not a cost-effective way to get the Pathfinder Mythic Skin.

Respawn offers this as an option for those who only want a couple of items from the Collection Event and don't want to rely on Event Packs for the items they desire.
Otherwise, the other three options are up to you. If you're swimming in Crafting Metals, you could purchase event cosmetics with these and it won't cost you anything upfront. But most players won't have that many Metals on hand. Instead, you could purchase some of the event using Metals and then buy Event Packs to complete your collection.
Of course, Heirloom Shards are also a rare item. They have a super low 0.045% drop rate and theoretically cost you 500 packs (50,000 Apex Coins) unless you get lucky. But if you have them and don't like the event cosmetics, this is another way to get the Pathfinder Mythic Skin with no additional cost on top of what you've already spent on the game.
🎯The cheapest way to get the Pathfinder Mythic Skin in Apex Legends
There's a secret method to save some coins and bring down the cost of the Pathfinder Mythic Skin. You'll be purchasing Event Packs to get the skin using this method. Here's how to save some cash.
Head to the in-game Store.
Purchase the two Techno Terror Collection Event Bundles, which cost 7,500 Coins each. You must do this before purchasing/opening any Event Packs as they come with Skins directly. If you unlock the skins, you can't purchase the Bundles.

This method saves you money because the two bundles cost 7,500 coins each, which is the value of around 10 packs, but you get 12 packs worth of items in the bundles. This brings your coin total down by 14,000, saving you $12.
You can also combine this method with crafting some of the 'purple rarity' cosmetics to further lower the cost of getting the Pathfinder Mythic Skin.