Here's the basic hardware you need to master music:

• A Computer (preferably a quad core or faster)
• An Audio Interface (which contains a mic preamp and instrument cable inputs)
• Studio Monitor Speakers & A Sub-Woofer
• An Audio Control Unit To Control Speaker Volumes (optional but  it makes life a lot easier)

If you're looking to get started real cheap, you could make a decent hardware only set-up for about $1,500.  High-end hardware will run you roughly $3,500-$4,500.  Still not too expensive.

See - Let Me "Personally" Step-by-Step, Show YOU How To Master YOUR Music!