I don't think you can go by what other people are saying about compnent life. For example I ride in all sorts of nasty condidtions and have a lot of steep twisty hills. I used to consume break pads and wear out rims every couple years before I went to dics on my commuter bike. Also no matter how much or little I ride I usually end up replacing my chain every spring. I climb standing a lot and wear out certain gear combinations so I'm lucky to use maybe two chains before I need a new cassette. I also seem to need a new bottom bracket every couple years but have never had a headset problems. Tire life can vary greatly with different types, brands, and models. And so on and so on. .... The point is that you will get different answers for how fast stuff wears out depending on who you ask.

In my opinion $1000 is more than enough for a decent commuter bike. In terms of what is cost effective I'd probably look at Bikes Direct bikes, or maybe even stuff that Nashbar or other discount sites are offering good deals on. The same goes for parts. I often look for decent stuff at overstock/older model prices. Then again I like bikes and I understand that money can buy quality and craftsmanship. Sometimes I just want what I want and am willing to pay for it.

But of course this is just me. You will get as many opinions on these things as people you ask. Keep learning and listening but do what most makes sense to you.