When purchasing a SharePoint solution customers are faced with many options. There are a number of SharePoint editions which vary in feature sets and prices. In this post I will try to share my experiences with this problem. Since there are so many options I will focus only on three major products: Windows SharePoint Services 3.0, SharePoint Server Standard and Enterprise. Other products like Forms Server and Search Server will not be covered in this post.

Level 0 - Windows SharePoint Services

SharePoint Services are the fundamental part of each SharePoint edition, biggest advantage being low cost (free for customers of Windows Server) and basic but very important collaboration features (listed in Table 1.)
For most small to medium companies WSS will be a great choice. It will provide your customer with great functionalities and decision makers will love it since it is free. If this solution gets adopted by your customer's IWs, you will probably have more opportunities for further customization and development.

Level 1 - SharePoint Server 2007 with Standard CAL

This is more mature and more expensive version of SharePoint. It will give you almost everything you might want from a collaboration solution. This product is very affordable, since its CAL is part of Core CAL and many customers have already bought it with their enterprise level agreements. Customers with such an agreement only need to pay for a server license.

Standard CAL will be great for companies that would like to:

• build a corporate portal on top of team sites
• create a central search site for searching information company wide
• would like to allow portal personalization (My Site) and company social networking
  

Level 2 - SharePoint Server 2007 with Enterprise CAL

This is the most expensive edition but it includes some very interesting features which are worth the investment. You should consider choosing this edition when:

• your customer wants to tightly integrate SharePoint with other business applications
• your customer wants to use SharePoint as BI tool or wants to publish Excel files as web pages
• your customer wants to convert Infopath forms to web pages

(1)    Source: http://office.microsoft.com/en-us/sharepointserver/FX102176831033.aspx
(2)    To be licensed for the Enterprise Edition functionality of Office SharePoint Server 2007, both the Standard and Enterprise client access licenses are required.