Do You Have to Pay to Play Diablo 3?

Payment Breakdown for Diablo III

• Initial purchase: Yes. Buy the base game (Diablo III: Reaper of Souls – Ultimate Evil Edition on console; Diablo III + Reaper of Souls on PC via Battle.net). No free-to-play tier.
• Monthly subscription: No. One-time purchase only.
• Microtransactions: Optional cosmetics only. Wings, pets, pennants, portrait frames, extra character slots, stash tabs. Zero gameplay advantage.
• Seasonal content: Free for owners of Reaper of Souls.

Summary

Buy once, play forever. Spend extra only if you want your Necromancer to have flaming skeletal wings.