plenty of DIY people can make anything audio and make something very special making them for commercial sale is entirely difficult. I know, my friends all ask me to make them audio gear. Building something takes time and trial and error research.
You also have to have the gear (source, preamp and amp) to hear and appreciate the differences in designs. To my ears, most of the manufactured stuff most people have listened to is nothing special. You get different flavors from your components but not much in sound improvement (generally speaking), such as resolution, dynamics, sound stage, tone, etc. Most people have never heard that from their system so they buy and sell components, cables, etc. to find what they think they are looking for. For example I build a preamp with no caps in the signal path. Every cap has a sound so what works in your system may not please someone in their system. I don't use caps in the signal path so that is one area that most people have never experienced to explain my point. So until you have the gear where you can really hear the differences, your comparisons of higher priced gear to what you have heard or how the higher priced gear sounds can be misleading. Happy Listening.
