7th edition foils have always been greatly sought after due to their rarity. As of this writing, you can’t even find 7th edition foil Underground Rivers on Amazon. They’re pushing $32 now, an increase of about $10 practically overnight. While Underground River doesn’t see tons of Modern play and the other foils haven’t moved much, it’s not a bad idea to watch the foils of these pain-lands, no matter the edition.
Attrition is a very strong Enchantment in Commander, played in a wide variety of decks that play Black. Urza’s Destiny foils spiked after the release of Fate Reforged to $30 then fell back down to $15. They’re just getting back over $20 over the past week, so if you’re looking for a foil copy of this card, now is probably not a bad time to grab one.