Players can purchase loot crates in PUBG with Battle Points (BP), but it is always randomised to which type of loot crate a player could receive. Also keep in mind that all of the cosmetic content rewards provided in them are also randomised. Aside from the variety of loot crates offered by the game, one such variant obtainable from BP purchase is the locked crate which requires specific keys for them to be unlocked.
The kicker to locked crates is that the only way to obtain these keys is by purchasing them at the PUBG in-game store or the Community Market in Steam. Either procedure will require the player to spend real-life currency, while the latter may have price fluctuations depending on the rarity of the keys. Players also sell their obtained locked crates in the Community Market at varying prices. PUBG Corp. expressed in their dev blog saying that they have been thinking about this carefully and want to steer clear of revenue models that fail to satisfy fans. PUBG will no longer drop locked crates from BP purchases on 18 December 2019, but the remaining ones sold by players are still purchasable from the Community Market. Keys may still be purchased only if the player have a locked crate in their inventory. (Source: PUBG Dev Blog)
