The trad gang has 38,000 members and probably twice that many lurkers, I would guess 5% make bows, mostly glass lam but a lot of wood bow guys as well. When they hold the St Jude auction there are a bunch of folk from all over the world looking for stuff to bid on. If I made 50 of these things someone out there would want one and they would all be auctioned.
I did my own fundraiser last year for the same cause. I posted the donation for a a gizmo offer here, Stickbow, Trad Gang and a Facebook selfbow group. I sent off 30+ gizmos in a month, I wrapped it up because I was tired of making them.
Gizmos are very easy to make but some folk want one from the inventor complete with my brand on it, some just want to donate to a worthy cause and some folk don't want to be troubled by making their own.
Bow making is a lot more common than one would think, it tends to be localized like the bunch around Twin Oaks. Where I live there may be 5 or 6 bow makers that I know of in town but I am always hearing about someone's uncle, grandfather or some other relative that makes their own bows but don't mix with the internet crowd or shoot tournaments.
I may have auctioned off 75 gizmos, I have given away twice that many, both online and to guys I see at tournaments who are shooting a selfbow they made.