Halo 5: Guardians REQ Packs can be purchased for real money 

Microtransactions in Halo 5: Guardians multiplayer will be an option for players who wish to skip earning points to purchase REQ packs. However, only cosmetic items acquired through the REQ packs can be used in the Arena experience.

Over on Halo Waypoint, 343 Industries' studio head of internal development explained how the real-money option will work.

"The Requisition System (REQ System) in Halo 5: Guardians rewards players across both our multiplayer experiences," Josh Holmes wrote. "Players will earn REQ Points after each match in Arena or Warzone multiplayer, which can then be redeemed for REQ Packs. Each pack contains a variety of requisitions in the form of unlockable weapons and armors, skins, assassination animations, and more.

"In addition, players will receive REQ Packs as rewards when they level up their Spartan Rank and complete Commendations across multiplayer."

All REQ content in the game can be earned through the course of play in multiplayer as purchasing REQ Packs is offered as "a matter of convenience" only. A portion of the proceeds will be tossed in the prize pools for the Halo Championship Series.

Holmes said cosmetic items are only allowed in Arena because 343 wants to "ensure that all players" start with the same weapons and abilities which promotes balanced, competitive play.

"In Warzone, we wanted to give fans even more variety and choice in how they play," he continued. "Within Warzone, you’ll have the ability to deploy a multitude of weapons and vehicles from your inventory of REQs throughout a match. These requisitions are governed and balanced by Warzone’s in-match REQ Level and Energy systems, which are driven by player and team performance within the mode."

343 hopes the REQ system will keep gameplay fresh by rewarding players with a steady stream of content. More REQ content is planned post launch in order to provide "new toys" to play with.

Halo 5: Guardians is out October 27 on Xbox One.