Minor DLC with no randomization involved. New items, equipment, abilities, etc.
It's Not Gambling, We Swear
Loot boxes with randomized contents, buyable with real money
Infinite Money Hole
No upper limit on in-game purchases
Changing The Game
Content with gameplay-altering effects, buyable with real money
But First, You'll Need A Contract
A game-specific paid subscription service
The game sells a premium currency named "Kakao Cash", or "KC", which can then be spent on all manner of things in-game. KC is bought at a rate of 10 KC per dollar, with no discounts for buying larger bundles. You can also sell things that you purchased with KC on the market. This is somewhat limited by the amount of listings you can have a week.
There is a bottomless ocean of things to buy with KC in the game's "Pearl Shop" (check the pearl shop link in the external links section below), including pets, mounts, weapons, equipment, increased inventory/storage space, and much, much more. Pearl Shop items on the U.S market don't permit you anything you can't otherwise attain with in-game currency.
The game also sells various "pay for convenience"-items. For example, the "Blessing of Kalmasylve" increases the drop rate of items and the recovery rate of your character's energy while it is active (7-15 days, depending on how much you spend). The Artisan's Memory, on the other hand, dramatically increases the efficiency of a single repair when repairing an item's durability.
There is a "Value Pack" that is effectively a premium subscription, speeding up progression and "permanently" dyeing gear (until the pack wears off), among other benefits.