RSP for custom duty

Hi,

I am importing Auto spare parts (Chapter 87) and facing  big problems while clearing.

Custom officer is increassing the RSP value to 2.5 times the basic cost at which I can not sell it in the market.

Now the overall duty comes to more than 45%.

Is there any rule to fix a minimum RSP of 2.5 times the basic cost?

Regards,

PJ