Hi I wanna build a gps tracker for car using arduino atmel micro my question is
Do you think is possible do it at a low price?
like a sell price around 40 usd that is the price I see it in amazon, or is a crazy idea ?
Thanks for yours reply 
market is flooded with these. The cheap ones put the application code inside the GPS receiver, on the same MCU as runs the GPS algorithms.
Try a different product!!
Rule of thumb: Retail price is 400% of the BOM cost.
To allow for overhead, manufacturing, sales, G&A, distributors’ markups, warranty and so on.