One realisation for those building a home recording studio: there are so many choices. It may seem easier to pay Noel Gallagher from Oasis to do the work.
The second most startling realisation is that you'll pay through the nose for some of the gear. One AKG microphone can cost a few thousand pounds, and audio mixing boards are horrendously expensive.
Fortunately, if you already have a high-powered PC (or know how to build one) with a dual-core processor and plenty of RAM, you already own a potential recording studio.