I don't really intend to appear harsh but in his own words your "friend" has only been doing this for just over 12 months and he started in a college dorm
....yeah, I know we all have to start somewhere.
My point is firstly, that he, and a lot of other "custom drum makers" ARE NOT making drums, they are assembling and finishing pre-manufactured components. In reality, it is no different to assembling a model aircraft..........have patience, think each step through before actually proceeding and have the desire to complete something that you can be proud of and chances are you will have a great end product.
Second point............these guys are not doing anything that is not within the realms of possibility for the average drummer, or many other people.
Third point...............give 20 guys a Keller shell, all supplied with the same generic hardware that's flooding the market
from Taiwan, same heads, etc., and the necessary facilities to cut bearing edges and snare beds, etc., and the biggest difference you may hear will be due to the bearing edge profile, variations in timber characteristics, external infuences and definitely not to be ignored is probably the most important factor...........our own individual perception..........it is a quirk of human nature that when we see an item that, for whatever reason, we are attracted to, more often than not, we perceive that specific item to be "better" than any other "similar" item regardless of whether there is in fact any real difference.