You can't tell me that every once in awhile some sprues get messed up and they go into a big bin and eventually they get remelted.
That's what normally happens, AFAIK: badly moulded sprues just get ground up and put back into the hopper that feeds the moulding machine.
There's such a thing as customer service.
I don't know how it works in the USA or Japan, but here in the EU, if there's a problem with a product you bought (like, say, a missing or damaged sprue to a kit), then whoever
sold you the product is the one legally responsible for correcting the problem — not the manufacturer. Of course, the seller can turn to the manufacturer to fix the problem for you, but technically needs to do that for you, not just refer you to the manufacturer (though that last bit is what often happens). And, naturally, the manufacturer can be lenient or decide to be customer-friendly and fix it for you when you ask them direct without going to the seller first, but they aren't
required to.
I for one think all these kits are way overpriced.
There's an expression in Dutch:
Wat de gek ervoor geeft — literally "What the fool gives [pays] for it". We're talking about a hobby, which can be as expensive or as cheap as you want it to be. Manufacturers will charge whatever people turn out to want to pay for their products, because they clearly have the money to spare for this lark.
All of that said, as I mentioned earlier I do think the ¥3600 is rather a lot of money for a single sprue. Looking at
the instructions for their Fw 190 kit, though, I see they cost substantially less than that, so I'm guessing that price
does include postage: