DIY Amp Preamp building

I just popped on a Dodd Audio preamp . He is a one man operation . From reviews his preamp is comparable to really expensive gear for a fraction of the price . It makes me wonder about what's inside all the gear i have owned/own. What am i paying for . How much is going to the marketing ,dealers,ect... .Anyone in MN build tube amps ? If so let's talk about building me one .