IT's not specific items, it's just an easy formula, for above +30 the formula is bonus squared times 200. so, for a +200 spellcraft item it'd cost 8 million. Let's go level 100 wizard. Max ranks 103, skill focus and epic skill focus gives us +12, Int 18 +20 levels + 26 (that epic feat that increase Int one) + 5 through wishes and we have a 81 Int or +35. So that gives us a +360 to spellcraft. Not enough but you can easily increase the spellcraft item, and I didn't include an item that gives a bonus to Int.