This hobby is going wherever you as a pen turner/maker/artist or whatever you want to call your self is willing to take it.
The quality triangle comes into play here. Speed/Cost/Quality. You can only pick 2.
If you want to view this from a pen sellers perspective, you can chose to go the PSI route and turn fast product out the door at the expense of quality control. Your costs are less and a large portion of the work is already done for you to the tune of them even sanding your tubes for you now.
Alternately you could also choose to go the route of buying from suppliers like Richard Greenwald, Indy~Pen~Dance, or The Classic Nib and integrating their offerings of clips, bands, nibs, sections, transmissions, etc... into your own designs. But going this route takes time and your selling prices will go up accordingly and you're now selling to a different demographic and likely at a different quality of show.
For me, the PSI pen kit of the month club got old for me within my 2nd month of turning pens. I have settled on about a half dozen staple "kits" for my general lineup and use those to get my foot in the door and segway into higher end offerings. I do buy kits to fill orders and I do buy kits to populate the show table, but they are a segway offering for me to fund the custom work until the custom work becomes self sustaining.
Now if you're doing this purely as a hobby, then I don't believe there is a right answer other than to do what you enjoy.