Here are the Exchange licensing options, and associated prices. Exchange is licensed per Subscriber Access License (SAL) with several options available.
Hosted Exchange 2013 Standard SAL
This product provides Outlook Web Access, Internet mail protocol access – SMTP, POP, IMAP and Web browser. Also included are use of Personal Mail Folders, Personal Tasks, Personal Address List, Personal Calendar, Personal Contacts, Single second level Personal Domain, (all not shared with others) and Global Address List, MAPI, use of Shared Folders, Public Folders, Shared Address List, Shared Tasks, Shared Contacts, Shared Calendar, Group scheduling (including viewing free/busy times of others) and Mobile Device Access. $2.50/mo.
Hosted Exchange 2013 Standard Plus SAL
This product includes all the features of Exchange Standard and the installation and use of Entourage or Outlook client software. $4.00/mo.
Hosted Exchange 2013 Enterprise SAL
This product includes all the features of Exchange Standard. Also included are Unified Messaging, Compliance Management, Exchange Anti-Spam, Forefront Anti-virus and Exchange Hosted Services Anti-virus/Anti-Spam. $5.95/mo.
Hosted Exchange 2013 Enterprise Plus SAL
This product includes all the features of Exchange Enterprise and the installation and use of Entourage or Outlook client software. $7.45/mo.
A Subscriber Access License (SAL) is required for each unique individual user or device that is authorized to access or otherwise use the licensed products. When using the SAL option, there is no need for a separate Server License. Examples of products licensed with a SAL: Microsoft Windows Server®, Microsoft SQL Server™, Microsoft Exchange Server, Microsoft Office, and Microsoft Dynamics™ business software.