http://www.d20srd.org/srd/epic/magicItems/basics.htm
"In general, an item with even one of these characteristics is an epic magic item."
from the list-
"Has a market price above 200,000 gp, not including material costs for armor or weapons, material component- or experience point-based costs, or additional value for intelligent items. "
It does have some verbiage about the x10 cost multiplier, but that's for "If the item gives a bonus beyond the limit allowed in for normal, nonepic magic items..."
But I have honestly tried my best to completely ignore the existance of the published epic rules.