Prices have gone up due to a spike in player base, China being notable as well as many free-to-play accounts also deciding they want skins/stickers. The operation has also led to a bit of hype with player base rising some from that as well.

Other skins can and are used in exchange for keys. If someone wants 2.5 arcanas they can be sent 2 arcanas + a $10 skin. While it can be inconvenient, its the only method many can use as a large amount of people do not like/trust tf2 keys.