I live in Japan and yes, I paid a bit over $400 for the swing arm with the kit to convert to fit MC21.

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Seems a lot, I know - but I have seen these swing arms sell for $300 without the MC21 fitting kit and it would have cost me more than $100 to get one made. I don't mind sharing the dimensions if they'd help your intended conversion, although bear in mind you'll need a wheel and other bits too. The assembly as complete would be needed.

I actually have another MC28 swing arm, but I bought it for the hub assembly, as I intend to use this on my VFR750FL - to make the single lock nut conversion so I can then fit carbon fiber wheels to it.
I'd be willing to part with that swing arm and other parts that came with it, just not the hub assembly, which probably isn't a lot of use to you...