Seems like massive overkill. You have to remember, you're not paying 50 euros for ONE keycap. You're paying for 50, or 150, or however many. That seems like an ENOURMOUS waste of resources and space.
Not from my point of view, it's essentially 50 pieces of small plastic, think of it as a single toy, or a small lego set, less plastic than that
It's apparent we all value and praise our keyboards and keysets a lot, try to look at it from that point of view
What I would suggest, is to come up with an ideal mockup that covers most users. Thats what radio_killah and did with the modsets we ran. You could then try and spin that set to gb runners if the time comes. I think the hardest part about putting together a GB is determining which extra keys everyone wants. If you are set on this idea, I think it would really help GB runners if you did the legwork for them in providing a good mockup that covers most peoples needs in a set.
GMK has lowered their prices and MOQ recently, so I don't see why this would be an issue in the future from a price standpoint.
Most keysets lack 1 or 2 keycaps to make them compatible to a subset, with the above calculations it's 50-100 euros
When you combine these subsets into a larger "irregular interests" set, there might be 10-12 keycaps, at that point, it becomes a small GB, money transfer becomes an issue, logistics becomes an issue, feasibility becomes an issue, so I don't favour that idea much - running a GB isn't easy, but ordering keycaps are, that's my point
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Ideally, for example, MassDrop could add such a feature, there could be multiple compartmentalized interest packs, for example, "A Bumped Homing Kit", a "Small Spacebars Kit", an "OSX Kit" - people could pledge at $20 per kit, while the cost is $2 per kit, then they would get 10 packs instead of 1, and 15 kits would sell. For the same set, if 20 people join, it could be $10 per kit. So basically, at sub-150, people would pledge for 1+ sets - If the set somehow reached 150 MOQ, it would be no different than a regular add-on
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What I'm proposing is easier for <10 people, at >10, shipping/money becomes a burden, pay $50 for a bunch of keycaps, the leader of the small-run could ship keycaps to <10 participants, give-away your extra keycaps at a gathering, keep them as keepsakes, aftermarket them if you have the time/energy/interest, doesn't matter