There has been a lot of stupid posts around here lately but this one is my favourite so far. I'm honestly surprised that you managed to jump to a conclusion that is so incredibly wrong.
First of all, as you can see in this very thread, people are already receiving their rewards. Now, it might not be your specific tier (or for your specific items), but that's because they are all in different stages of production. YSnet have explained this to backers multiple times and have even released a Kickstarter Update to address this. They listed items that would be shipping with the game, and items that would be shipping post-launch as they are still being prepared:
Second of all (my favourite part of your post), they aren't using fucking sales income to fund the backer rewards... Fuck knows how you managed to arrive at this conclusion?!? Think about this for just 15 seconds as if you were in their shoes. You have promised ~80k backers rewards that they paid for. Would you:
A) Set aside the money required to produce said items.
B) Use all the money upfront on game development, and then shit yourself later on, hoping that you make enough money from game sales to make said items.
Hopefully, you went with A, because that is the correct answer, and the one that literally anyone would choose, as did YSNet:-
Lastly we arrive at the sales of Shenmue III but there's no point in talking about it "as we know, the sales have been brutally bad". No we don't know that! You don't know that, I don't know that! Nobody on here knows that! The only people who know about the sales numbers are YSnet, Shibuya Productions and Deep Silver.
Even if we did know the sales numbers, which to clarify,
WE DON'T (we only know physical of Japan and nothing of digital PSN, EGS, not to mention the rest of the damn whole world), we still don't know how much the game cost to develop, how much money was poured in, what kind of deals went down behind closed doors. Without knowing those, sales data is irrelevant because you cannot deem it a failure or success as you do not have the full picture. When Cedric Biscay of Shibuya Productions (the guy who made this game happen in the first place, and the guy who funded the game with millions of dollars of his own money) says that he is happy with Shenmue III, then maybe you should listen to him, and not some shit inconclusive physical sales in Japan!
Sorry to come off so blunt, but I feel like the there has been so much wrong information passed around the forum and the Shenmue community in general that stark words are needed to get the point across these days.