I was coming here to say this. Before NewEgg, the best way to buy computer parts was to show up at a conventions center or fairgrounds, firehall or community college for the next Computer Show. Buy some parts in cash from people who speak barely any English and then either take it all home and start assembling or hand it off to the ancient guy chain-smoking at the back door and pay him to zip-tie it together in 5 minutes for you.
Years and years of doing this and we only had one situation when we cracked the case later and found out the guy has swapped the parts we bought for used Dell components when we were at lunch. Always took them home after that.