our practice: we buy as cheap as we can with decent performance--as we have had several computers that got viruses and it cost a lot of $$ to get rid of some viruses. The more kids go online for lyrics, youtube, online games, etc. the greater the chance for viruses--at least in our house. We are not tech savvy, so we can only do limited things to try to get rid of the viruses--and yes, we had anti-virus software.
We pay under $500 and then just toss it in a few years--as upgrades have come out anyway. We did this for our desktop--bought it for $299, bad virus 4 years later, bought a replacement for $399 (just missed black Friday sales). I would look for a good deal after Thanksg. Also, my tweens/teens use Word and Powerpoint for school and that's about it. If you have to buy that separately, that will be an additional $100 or so--sometimes you can get a package.