Depends on what you're recording and what quality you're shooting for.
For a full 'one man band' thing, at the very least, you'll need a decently fast computer with lotsa RAM, a mixer, a keyboard or midi controller, ,midi converter, an amp, monitors, an extra hard drive, preferably a large computer monitor or 2 of them)... a mic if you want to do vocals or record acoustic. The sound card in the case of Macs you can just stick with the factory installed one but you can upgrade. Decent recording software will run you at least $500 and you'll need to buy some sample and loop CD's, cables and a couple of decent VST plug-ins like a reverb, compressor and a good VSTi synth. Plus cables, cables, cables, extension cables and powerbars and somewhere to set everything up.
If you want a decent sound when you're monitoring you need a decent stereo amp and some near field monitors and headphones..plus stands for stuff like the mic.

So basically, just add all that together & anything you pay above the basics will get ya better sound quality, more VST plug-ins, faster access and being able to run more plug-ins at once.. way better keyboard sounds and strings or samplers..monster cable, air conditioning for the hot summer months and a TV with a DVD to watch while you're doing boring editing... pizza, beer...