Exactly my point, Gary. You would pay a buck or a buck and a half. To make it economical, the price for that centerband would have to be at least $3. The Jr. Gent II in 10k is an $8 kit. Economics would dictate that the components need to be price at least 3x - 4x or why sell parts?
Since the parts of the kit are (2) brass tubes,(2) lower barrel couplers, (1) end cap coupler, (1) clip, (1) cap, (1) centerband coupler, (1) roller ball nib, (1) roller ball refill, and (1) spring. Starting with a 3X multiplier, you have a value of the components of $24. Subtract $1 for the tubes and $3 for the refill, since that's what CS USA sells them for. You now have 8 remaining parts where you need to get $20 out of them to make it worth stocking. $2.50 per component. That's not terrible for a clip or a cap, but what about a spring? Or a coupler?
If this were really such a great business opportunity, someone would have done it.