you mean that after exchanging for prize your rebirth also decrease?
if so it has advantage and disadvantage
for the advantage it can add more stats,
for the disadvantage we have the a NPC(Hero) exchanging stuff with high stats,majority of us rather trade using the items then rebirth as we can is use rebirths to versus each other for competition =D maybe the GM can organize a competition with a deadline for people who rebirths the most.