Sarthak-n:
And my device costed about $50 without a case and is performing well for the last week or so.
That's components only I may assume. Without assembly cost, packaging, etc.
Do you have the proper protection electronics in place that make it work reliably in an automotive environment? Which includes voltage spikes and reversals, lots of electrical noise, vibrations, large temperature differences (thermal expansion/contraction can ruin your connections), etc? Automotive is one of the most hostile environments for electronics known to man.
Retail price will be $300-500 based on that price (5-10 times the bill of parts, regardless of what version of dollars you look at - this includes packaging, development, marketing, distribution, shipping, retail markup, your margin, etc). That, assuming you can start production in runs of a couple thousand units. For smaller runs it's going to be more expensive.