It's in-game "DLC".
The content is already in the game, the only thing they are selling is you is basically just a key to unlock it.
Proof of this is that you can get the content locked out by the amiibos by hacking the game with cheat codes.
If it were proper DLC, like the Expansion Pass of BotW, you wouldn't be able to spawn the DLC-only items, like the new Korok Mask, etc, without the update.
Amiibo DLC is another story.
Simple as it is, if Nintendo cared enough to make a digital-only version of the amiibo keys, we wouldn't have this issue.
If they did, I would buy the set I want by just paying a shabby amount of money into it.
But since all of these things are locked behind things which are:
- Subject to waves/games.
- Subject to stock
- Subject to preorders
Your chances of getting said item get diminished by a lot.
Not even taking into consideration scalpers, since those are another side of the coin as well.
And yes, while you can "finish" the game without said content, I am one of those people who likes to get all of the juice as possible from a game (100%).
And guess what? You can't because amiibo shortage is still a thing, and since they are used only once to unlock one thing and that's it, paying 10+ bucks for one is a rip-off.
Nintendo is handling this Amiibo thing in a very shady way, same for the Mini consoles being released.
Sorry but I'm not one to fall for that greedy system, I might as well just get myself an Amiibo spoofer and my days of worrying about those pieces of shit will be over until Nintendo comes up with yet another way to ripoff people's money.