I`ve had quite some contact with foreign cards, thanks to the UK`s amazing traders (Cutting Edge) who go all round the world to ALL the big events and basically get you whatever you ask for ('Summer Magic' Wrath? Guru Lands? Blue Hurricane? they even got Splendid Genesis - I held it in my own hands so I know it`s real).
The most commonly sought after foreign cards are the first printings of Revised as they were black bordered, and therefore they are significantly easier to get hold of than the Beta versions (the only other place to get BB Wraths etc). Typically they go for a couple of pounds more than the WB stuff
ie: WB Wrath £4 ($6), BB Wrath £7 ($10)
Revised stuff from Asia is more valuabel generally. We don`t see much of it over here, and what we do see usually stays in the hands of the people who got it and doesn`t get traded around much.
Foreign editions of more recent expansions are not particularly more valuable than the english versions apart from a few key cards where top-level tournament demand is high, but then most traders know that you`ll happily buy the English version so prices aren`t too high. (except for Korean Cursed Scrolls, which were misprinted to cost only 2 to activate).
ie: Tradewind £4, Japanese Tradewind £8
Basically, some people like Foreign cards because it is like a status symbol (and can actually affect play, my teammate lost because he thought his opponent had cast Survival Of The Fittest - it was in fact a French Oath Of Druids, which begins with an 'S' and so was shocked to see a Thorn Elemental pop up next turn). Asian cards ARE more valuable - they are both much scarcer (esp in Europe) and they look top and confuse small children no end.
Me: "I`m casting
=+/?'@"
Confused Opponent "WTF does that do?"
Me: "Can`t you read? It
@="%`#, but if I pay another 3 mana then it also does
{#:'=*.
Opponent: "?"
Me: "It translates as 'you scoop up all your permanents, and if I pay 3 I get to take a card of my choice from your folder permanently'"
Opponent: <scoops cards and reaches for folder>
SLICK
If you still want to find foreign cards then Cutting Edge will help, but you`ll have to ask them about shipping prices to wherever you are (they are very reasonable guys. Tell them Sutty and Rigby sent you and they`ll sort you out because we see them every week at tournaments).
http://www.cutting-edge-collectibles.com
They really actually ARE the best traders in the world - ee remember when they started out small with a single folder, and now they rule the world.