I'm not a fan of games (we all have our flaws, don't we?), but collectibles and prints on various media are part of my professional field.
I read your post carefully and yes, you have the right strategy. Pre-sales of collectibles and merchandising are great triggers that work in two ways: 1) passion and interest in the item (in this case, the game) is palpable. 2) Source of financing without initial investment by promoters, since this is done through pre-sales.
What caught my attention in your post, and hence the purpose of this comment, was your mention of the obstacle of the large number required for printing. (“...if we'd set out to print 50-100k cards, which is usually the minimum requirement for higher-end quality printing services.”)
I made a phone call to a supplier friend (one of those who don't mind being bothered on a Sunday :) and, for this case, he recommended this company that does minimum print runs of 300, 500, and 1,000 copies.
The quality is guaranteed, as it is one of this company's great strengths, specializing in this type of holographic playing cards.
There may be other companies that do this, it's just a matter of research.
I made a simulated request for a quote for 1000 cards: they respond within 24 hours. I will add to this comment when I have that information.
RE: Cards