Why do Synthetic rounds cost more on RPKM than DRS-IAR and KTS?

Synthetic tips cost 30 on RPKM, and 20 on the DRS (the literal best weapon in the game, or at the very least top 3) and the KTS, another similar, slow fire-rate LMG. 

Why?

The RPKM is not broken. It's not OP. It's not even among the best in its class. I really want to try the piggyback reflex on the new skin but I cant because my build doesn't fit bc Synthetic tips are super expensive on this weapon specifically. Please reconsider.