PayTm is good only for those who are very tech-savvy and are aware of prices of a lot of products.
One needs to be pro-active and verify the correct prices of products before paying through PayTm. Yes, PayTm does have provisions of discount but you really need to know the discount the actual company website is offering.
So, a lot of verification needs to be done before choosing PayTm or else you will end up paying more though the website will show that you been offered some discount.