Not to mention that very few people aren't already using a computer for something. It's easy to forget that a PC isn't just a gaming platform - it's used for work and leisure all day long.

Might as well combine everything in one system.

He's right though, if you want a full PC, the monitor will add around $150 (not sure on US pricing) on top.

There is a big difference between a standard keyboard and a keyboard for gaming. Especially since most standard keyboards don't allow you to "enter" more than 3 keys at a time, which is somewhat needed for PC gaming.

Mouse wise you can roll with that 90's trackball one but why? If you are going for a gaming PC you will want a decent mouse instead of ruining 50% of you input on a shitty mouse.

Speakers are important, but a cheap pair will do. I personally use a headset which would cost more.

And once again with a monitor you arent going to go out and spend $500 on a PC to play on a crappy 720p or outdated monitor. $180-$200 for a mid-range non-3D 60hz 1080p monitor. And using your TV as your monitor might sound good, but you don't want to do that for 100% of your PC use.