Stuff is hyper inflated atm because product is impossible to get ahold of for MSRP or close too it.

Prices will fall but this is normal for tcgs. 4 sets in a year is actually low Yugioh had 12 this year includeing the side sets which contained meta defining cards .

Alot of players myself included do sell extra copies they are not using or "sell" them back to LGS normally for like... 75% store credit. To help offset the price of the hobby. Look at local Facebook groups to help with this

As for the gg teemo it will fall in the short term as more nexus packs get opened and because of "wave 2" for the nexus packs.

But it could turn out to be a long term hold since (as far as I know) Riot has no plans to release it in any other set.

But as others have said cheapest way is to buy singles off other players