hi
while you buy the material , i suppose you buy from other state by paying the IGST
in such case you have 2 options
Option 1
Pay the IGST on export value of 130 to government assuming the IGST Rate of 18% you will pay to Governemtn 23.4
in this case the customer will be billed only with 130 - and you will receive this 2 $ in convertible forex
in this case you can use the input IGST of 5 Rs. and pay net of 18.4 and apply for refund of full out put tax of 23.4
Option 2
Do not pay anything on export as Zero rated and then apply for refund of Input credit of only Rs.5
IF you have bought from same state i.e by paying CGST / SGST then you have to only go for refund application subject to conditions
Thanks