I got most of my equipment when I was still working in radio -- it's about ten years old now. It's traveled with me to recording sessions, conventions, and three different houses in two states.
The microphone was $40 (it was on clearance or somesuch), the board was $110 (on sale), the stand was I think $30-$40, and the pop filters were $6 for a three-pack. I also spent about $150 on cables -- you'll probably only need to spend a fraction of that (one to connect the mic to the board, and one to connect the board to the computer), but I have a lot of other stuff that needed to go in and out of that board at the time -- other audio sources, my guitars, etc.
Honestly, if you have a good microphone and a good cheap stand (preferably one that doesn't sit on the table, as mine does), you can get an inexpensive board (the 4-track version of mine cost $75 at the time) and call it solved. The microphone is the most important part, followed by your sound card. My old Dell laptop had a great line-in, but the Toshiba I bought after it was pretty meh (very fuzzy and clipped). That's why I had to buy the computer, which was actually the most expensive thing -- $300 (I already had the monitor).
I don't have any soundproofing, but that stuff's not too expensive -- or you can just use foam from packages your IT guy gets. Depending upon what kind of room you want to record in, you may not need any; I'm in my basement, and as long as the water isn't running (the laundry room is in the kitchen, just above me) it's perfect. I do have to noise-cancel the heater in post-production, but if you can pick out on any of my StarShipSofa narrations when I did that, then you have better ears than me. (I can sometimes hear it in the ones I do for EP.) My basement is half-drywall and half-wood-wall, with a carpeted floor and an industrial-style drop ceiling.
Finally, spend the money to get a good pair of headphones. Earbuds -- especially iDevice earbuds -- do not cut it. I prefer these (
http://www.amazon.com/Sony-MDR-V150-Monitor-Series-Headphones/dp/B000092YPR). They're comfortable, inexpensive (price has gone up $6 since I started using them in 2002, for a grand total of $21), and easy to get online. I have three pairs right now: one for work, one for home, one for the gym.
I'd say you could put together a little home studio for under $200, if you already have a computer that can bring in your audio and run your editing program.