I built about 40 rods in my day . Most pre graphite or it was new , expensive ,and not great.
I enjoyed doing it and still use my long drift rods to this day .
I keep wanting to build another but first , you can get any premade you want . And a custom built is not that much better . Or even worse if you dont set it up correctly with the right components and guide placement etc .
Second , to build a decent rod will be double to quadruple what a premade is.
Blank
Handle set
Guides
Epoxy
Thread
Finish
And non of this is cheap .