In short: You don't have to "buy" the base game anymore, but you do need an active subscription to play most of the content.
To level past 20 and access almost all legacy content, you must pay a monthly subscription fee (typically around per month, with discounts for 6 or 12-month commitments).
: You cannot join guilds, use the Auction House, use the mailbox, or whisper players who haven't added you as a friend. Currency Cap : Your gold is typically capped at 1,000. 2. The Subscription (Access to the "Base Game")