Haven't ordered any parts from the US but depending on parts and shipping costs and the current exchange rate, parts from US end up priced roughly the same as in Japan (at least on Amazon).

For example, a 4070ti:

Japan JPY128,000

USA USD 916 or JPY 132,000 (with shipping and deposit for customs).

Another thing to take into account is warranty and if they will honor locally or if you have to ship back to US (either Amazon or manufacturer side).

I already see some on Amazon. Are these not the same?

https://www.amazon.com/MSI-GeForce-RTX-4070-12G/dp/B0BNWFM7MZ