Expensive tends to be better but what types of parts or accessories do you not mind or even prefer if they're on the cheaper side? I don't care about expensive mouses and keyboards anymore even as someone who plays fast paced games somewhat competitively. I've bought expensive mouses meant for gaming before but now I use a $15 compact optical 500 and it's the best mouse I've had. The reason I like is it cause it's very small and light so it's easy to move quickly. The only down side is if you move it extremely fast it doesn't register. I've always like extremely simple keyboards too without any extra buttons. An inexpensive computer case is okay to me as long as it's functional. On the other hand I like a good mouse pad. I've bought some pretty low quality ones before so I'll spend $10 or $15 on one that I think is good.
Same as you, I don't care about the price when it comes to keyboard and mouse. As long as they fit my preference, they can be as cheap as they need to. Of course, they must also work. Other than these, I think are computer speakers and sound card. I don't really watch or game on PCs other than watching videos on Youtube so they can be whatever as long as there's sound coming out of them.
I am the same way. I don't really care about mouse quality as long as it works, and I suppose I also am the same way when it comes to the other minor accessories such as wires like HDMI cables. I've had the chance to pick from HDMI cables in varying prices, and I thought I would start with the cheapest one first and work up from there if it eventually turned out to be unsatisfactory, but fortunately, I never had to move up the ladder because the cheapest one I bought did the job and I even still am able to use it now a whole year after I first bought it.