Its been fairly much a perfect storm affecting many components.
1. Getting a quality PSU has been fairly difficult since Feb/March because of covid shutting down China at that time and increased demand making it hard to catch up
2. Ram has been easy to get but apparently they are expected a rise in price in the short term owing to issues at factories
3. NVME/SSD the good news, easy and cheaper to get in 2020
4. GPU, shortage of capacity to make chips and some associated material, eg substrate. Caused by increased demand, Nvidia claim that they are selling about double the number of GPUs that they were the previous year. Not helped by lack of supply by AMD as they have other products to make with their capacity eg game consoles and CPU. Car makers are closing factories as they can't get computer chips to make their cars. So different industries fighting for CPU/GPU
5. Transportation issues, less planes flying and bottlenecks at UK ports making it harder and more expensive to ship items to the UK. Apparently at one point the UK government was paying £1 million a day to store 10,000 containers of PPE at one port. Shortage of empty containers being taken back to China to ship goods in.