TechRepublic have an interesting article on building a great Linux PC for under $1000. Although it's clear the article refers to US dollars, which in price terms is usually lower, the prices are mostly comparable with what we pay in NZ.
My last couple of build experiences were different. I built a low cost system using a Gigabyte H110-S2H board, my usual choice of a Pentium G CPU, and 8 GB of RAM for around $300 about 3 1/2 years ago. I think initially it was installed with Windows 10. It was cheap because I recycled a case, power supply and hard disk, so I only had to pay for the board, CPU and RAM which cost about $100 each at the time. The board was taken out since then and put into a different chassis and it has been repurposed for video playback, because it only has 2 DIMM slots. I must have been really strapped for cash at the time as all the other systems I have built used slightly more expensive board with 4 DIMM slots.
Last builds I did were buying a pair of Gigabyte B250M-D3H boards and Pentium G CPUs for a total of about $500, just about 18 months ago. I had planned on getting newer B360 boards and Pentium Gold CPUs, but there was a shortage of the CPUs at the time, and I discovered Dove Electronics, a wholesaler we used to use when I worked in high schools, had only two of the B250 boards left, probably the last stock of this model in the country. I managed to get these shipped to me along with the CPUs and 32 GB of RAM for one of the boards (another $500), then rearranged a whole lot of things. The aforementioned H110 board being taken out of a chassis and replaced by one of the B250s with all the new RAM, and the other one going into a new system with some RAM from the H110 board (this had had 16 GB previously but that was split between it and one of the B250s).
The oldest thing I have here is a Gigabyte Z97 which is the computer I am writing this on, with a heap of RAM, I can't quite put a date on when I got it, but it is still going strong and probably has years of life left in it unless the board blows up or something. Because it has still got heaps of performance for everything I can throw at it. The hard disks are the only parts I have had to replace and as one has been a bit finicky lately I might have to scrape together some cash to replace both of them soon which is a bit stiff with my current resources. This system is also the only one of my computers (apart from the Mini-ITX system) for which I have actually purchased a chassis, all the others being recycled from schools. The B250 that had only 8 GB recently got a boost to 16 GB which cost around $70.
Anyway going from the article, pricing is pretty similar and if you had to buy everything new it soon adds up. The only really different cost I can see in there is for RAM; 32GB at current pricing in NZ is about double what he quotes ($275 at PBTech, which itself is a fair drop in price from what I paid 18 months ago).
Building your own PC is actually pretty straightforward and well worth while. The most complicated task you would typically expect to encounter is installing the CPU and fan, and I have never had any issues there despite the potential for damaging the chip or board. I usually build my systems on a wooden base on a table (nude) and then install them in the chassis once I have verified everything is working properly.
Considering that in 1997 my first serious PC cost nearly $4000 from a shop (with a cheap inkjet printer) it is amazing that the cost of parts has come down so much (no allowance for inflation). Even having a shop build you a PC today wouldn't cost anything like that much, maybe $1500 for a system built in NZ. Of course some companies are having systems built to order overseas and then shipped directly to the customer. If you use Windows you can get it for next to nothing with a shop or OEM built PC, the retail edition of it that you can buy for adding to an existing computer being a bit pricey (I have one here for the one and only Windows computer - the Mini-ITX system - that I still use occasionally for compatibility reasons). Running Linux on all my home built systems takes the OEM licensing cost advantage out of the picture completely, besides all the other benefits that Linux brings.