By the way, the Super CD auction just ended for 8,750 yen ($113), and the DUO-R for 7,250 yen ($93). Pretty average prices, but by the time you factored in shipping you'd be looking at around $200 for either set up, plus whatever you'd have to pay to a proxy service.
Here is what I estimate:
Item: 7250 yen - 93 usd
bank transfer fee (if any) - 2 usd
japan shipping - 10 usd
celga fee - 10 usd
international shipping, cheapest (ems/airmail/sal) - 50 usd
Total: 165 usd
This one:
http://page6.auctions.yahoo.co.jp/jp/auction/f106065528
only went for 3200, which using the above numbers comes out to: $114, albeit with an untested cdrom
Well I'd say your numbers are a little off in regards to domestic and international shipping, but feel free to give it a shot! But I'd just warn you assume the system is broken in some way. Even if it is listed as tested, this often means that it powers on or displays something on the screen. Often DUOs have audio cap problems. Not the end of the world, but by the time you pay to get it recapped or repaired, you'd be in over $200 total, and for all that money and hassle you could probably just buy a refurbished one locally for less. Someone sold a recapped, region-modded DUO-R for around $200 on here recently. If a CD based system is listed as untested on YJA it's safe to assume it doesn't work at all.
Not saying YJA is a bad place to buy stuff, as I buy things off it all the time, but be careful as you might end up out of a lot of money to get a system with issues. This is why I buy systems for low prices, get them repaired, and test them extensively before I would consider selling them. That way someone doesn't here doesn't get burned with an unreliable system.