Well, $5,000 is way too much to spend on a computer that will be out of date in 2 years. But why stop at $5,000, you can spend $10,000, or more. Those kinds of builds are what a friend of mine calls "Taj Mahal" builds. It's for ego or vanity or for a magazine photo shoot, or to win a contest, or some other reason to impress people other than performance. Of course, if you're just a filthy rich person with tons of cash on hand, then don't hesitate to spend $5K.
Otherwise the rule of thumb that's been true for about the past 10-12 years is still true. A top-of-the-line gaming computer is going to cost $1,500 to $2,000 (not including monitor, speakers, mouse, and keyboard.) Right now, we are in one of those weird points in the product cycle where the most cutting edge PC components cost more than normal, because DDR4 just came out, and so did the X99 mobo's. So a cutting edge computer will set you back $2K right now. But in 6 months, it will go back down to $1,500. And you'll have 16GB of DDR4 RAM @ 4266 mhz (heh, Cas Latency = 28).
So bottom line, your "hard limit" should always be $2,000. And if you are at all bargain conscious, your real limit should be $1,500, or even $1,200, but that's if you're a really good shopper. Regardless of your shopping skillz, though, a $1,500 computer will do everything and anything you need to do, and it will last 2-3 years before it gets out-dated.
