Data compression is Enterprise Edition feature. There is a nice article written by MS:
"The data compression feature in the Microsoft® SQL Server® 2008 database software can help reduce the size of the database as well as improve the performance of I/O intensive workloads. However, extra CPU resources are required on the database server to compress and decompress the data, while data is exchanged with the application. Therefore, it is important to understand the workload characteristics when deciding which tables to compress."
Usually CPU usage increase is negligible after compression. However, you get lots of other benefits out of data compression.
Buy Enterprise license:hehe: