It's a lot of mid-range parts/specs. It's modest at a modest budget. It makes me wonder if you won't be better-off just buying something semi-customized from the big OEMs (Dell, HP, etc).
Building your own rarely saves you any money if you calculate in the value of getting something that is fully-sorted out-of-the box, and is guaranteed in-whole to stay going with a holistic warranty.
People build because 1) they enjoy the challenge/act of rolling-your-own; 2) they can optimize the build in a way that isn't common, whether through uncommon parts or overclocking; 3) they're control freaks; and/or 4) they like a totem to stroke. Be sure at least some of this is you before you commit to rolling-your-own.
It can be quite a big cost saving in the long run, maybe not straight away but further down the line you can upgrade with just a new motherboard, processor and ram provided you had started out with quality parts, case, psu etc.
The rationale seems sound on the surface, but I think the claimed "big cost savings" is dubious at best. Or just dependent on a certain set of circumstances that I'm not sure is relevant to this thread.
My experience:
Whereas there was a lone instance in which I simply swapped a CPU... my last 4 builds carried over-only PSUs and/or cases, and not even consistently. The simple reason is that I'm not a gamer, and generally build on a 3-to-4-year cycle. By the time I feel like I need a new build because the existing build is falling short of what I want it to do... not only do I need extra CPU/GPU power, but DRAM needs/standards have changed, socket standards have changed, my dataset has increased in size (through both accumulation and upgrades in my cameras) to the point where I need new storage solutions, etc.
I mean, my current build is 100% new with no carryover simply because by the time I came to near-completion... it was simply better to buy a new PSU to complete it and leave the old PSU in the wholly-complete and unscavenged old build to re-purpose it as a new version of my home server.
I mean, if you're a gamer and/or an enthusiast with a particular focus on having a maximized-system/personal-totem, and therefore update your build on a yearly (if not more-frequent) basis... then yeah, building your-own and swapping things out as better versions come along is of course going to be cheaper than replacing the whole thing at shorter intervals, with needless replacement of parts that do not significantly impact the user's use.
OTOH, if you're a photographer, and your processing needs grows with (or perhaps outpaced by) your need for storage... then the savings from parts carry-overs might be very little to non-existent.