price difference of exchanging new ring set

A) New ring set original price: $1758 for your this ring with a 5ct(9*11mm) DEF color radiant moissanite center, moissanite accents in all 18k white gold. ( 1 piece enagement ring +1 piece matching band) this is the new set ,size 8
B) the  origianl ring set(order 1813+ order 1600) was paid total $1419.7($1207.2+$212.5) , andcharged with 10% restocking fee $142 if exchange the new ring set.
C)client pay extra $480.3 if you need to go ahead below new ring set. Please kindly note. $1758-($1419.7-$142 restocking fee)
D) client need to return the old set before we send out the new ring.