According to your example
WAS
10+10= $20 @ 100 RD
20*1.25= 25$ @ 25% GST
$25*170= 4250 rupees
NOW
10= $10 @ 0 RD
10*1.25 = 12.5 $ @ 25% GST (if i am not wrong)
$12.5*285= 3562.5 rupees
So cheaper by 4250-3562= 688 rupees
I.e. 16.188 % cheaper
So a car that cost 30 lc before shoud now be priced at about 25 lac 20 thousand provided freight charges and clearing agents fees have not increased in the meantime. But as shipping charges are also in dollars so that cost would definitely have an impact.
Take the below example
https://batfa.com/shipping/9/suzuki-alto-2WD/12800/120
For Suzuki alto simple
$ 1290 are shipping and mariane insurance charges
Expense was
1290*170= 219300
And now would be
1290* 285= 367650
So the difference of 148350
Hence in the total cost decrease would be nearly 480000-148350= 331650 rupees
And thats not much
Also very likely that this difference would be absorbed by corruption profiteering and middleman mafia. The end consumer may or may not have any benefit at all.
Regards