When asked to run projects that utilize MSSQL as the database engine with the least cost, then you should be able to select from the various Editions of MSSQL that serves your need. This decision is based on your environment and what the project (task entails). See the following explanations below for the right Edition to use.

Five editions of MSSQL

• Express: This is the most basic of all SQL Server editions. It’s free to use in production, which makes it the best choice for independent software vendors, whose clients can’t afford the cost of a SQL Server license.
• Developer: This edition has all the features of the Enterprise edition, but cannot be used in production environments.
• Web: This edition is between the Standard and Express editions. It has features that Web hosting companies and Web VAPs can offer their customers to provide scalability, affordability, and manageability capabilities for small to large scale web properties.
• Enterprise: This is the most complete edition of all. With this edition, you have unlimited virtualization and high service levels for the mission-critical workload.
• Standard: This edition enables database management with minimal IT resources.