They charge what the market will bear. If their stuff stopped selling at current prices, then they'd lower them somewhat.
As for the I-400 vs. the Gato, I'd have to say that I nver plan on getting the Gato - simply because it would never fit or survive in my house. I have way too many kits I need to find display room for to take up that much space with just one, no matter how magnificent it may be. And with 2 dogs and 2 cats, and a wife with a lead featherduster, it would be like giving it a one-way ticket to the Bungo Strait.
Now the I-400, on the other hand...will have to wait. With a stash the size of a small country, I have plenty of work ahead of me already. But all things being equal, I'd take the I-400 simply because I've got a soft spot for the Imperial Japanese Navy. And the little planes would be really neat, too.