http://en3.babyran.com/extend/itemTransfer.aspx

【EP items upgrade to high level items】
Upgrade items will charge the price difference only.
EXP1: Fire Mask(260 EP) upgrade to God of Wars Helmets(4172 EP)
Charge will be 4172-260=3912 EP.
EXP2: Fire Pants(260 EP) upgrade to Elf Pant(788 EP)
Charge will be 788-260=528 EP.
EXP3: Damage Ring(837 EP) upgrade to Almighty Ring(3377 EP)
Charge will be 3377-837=2540 EP.

【Change between same EP items】
Charge will be 30% of the purchase price.
EXP1: Precious Fog Wing (White)(998 EP) change to Precious Fog Wing (Blue)(998 EP)
Charge will be 998*30%=300 EP.
EXP2: Godzilla Sword (Dex)(Freeze)(4000 EP) change to Anomalies Fist (Dex)(Freeze)(4000 EP)
Charge will be 4000*30%=1200 EP.
EXP3: Fire Mask(260 EP) change to Iori Yagami Mask(260 EP)
Charge will be 260*30%=78 EP.