Here at the the needs are comparatively simple. A CPU, RAM, motherboard and video card are the big ticket items. Chassis and power supplies are durable thanks to the ATX standard.
The old Cooler Master HAF 932 is a large box and it has seen a few power supplies come and go. The Corsair AX860i became problematic so the HX1000i is now handling the power needs.
Now that the MSI X570 board is installed there is interest in a better CPU. AMD consumer processors so not seem to have enough PCIe lanes to handle the typical workload. Due to some bad problems with the Ryzen 3000 processors, the outlook for the Ryzen 4000 series next year seem be be more interesting.
Power cables are used for the dive bays so only a single strand is needed from the PSU. This is done for easier cable management. The SATA data cables are bundled as well to simplify management.
The current SSD is the Intel 660p SSD which has been rock solid in use. The 512 GB capacity is increasingly inadequate so when the Intel 665p enters the market in 2020 an upgrade is likely. The move to a 2TB system volume makes more sense with a growing software stack.
Hard disks are low cost which is one of the reasons for their ongoing use. As bulk storage they will continue to be relevant for many years to come. SSD products have come down in price but they continue to be several times the cost per GB of storage.
Low cost second hand video cards are far more viable. The Sapphire RX 480 is a good example. At C$99 it was a bargain. More powerful video cards are available but prices vary considerably at auction.
Much of the hardware is made in China. Low cost of manufacture is desirable. Taiwan is home to Corsair. AMD has their logic made in Taiwan while nVidia has picked Samsung of Korea for their Ampere lineup. Intel has both domestic and international foundries.
Small items like SATA cables, fan extensions and similar are usually bought in lots of 10 or more. This usually reduces unit costs as postage rates have risen.
NewEgg and eBay are the primary merchant services.