When adding an item to cart, you'd expect the add to cart confirmation layer to show the details about the product you just added to cart (and not about existing cart contents).
For example when adding 1x Orange per USD 1.99 you'd expect the confirmation to exactly show the same information.
But if you've already got 3x Orange per USD 1.99 in the cart, the Add to cart notification will show 4x Orange USD 7,96 instead of 1x Orange per USD 1.99!
See above.
Show the amount and sum of the product just added to cart, irrespective of existing cart contents.
I guess this is a problem with current architecture, but I guess it means the architecture in Drupal Commerce needs to be aligned to better allow that. The current, unexpected UX shows it needs to be solved. I'd even see this as major UX bug. Clients are confused by this.
@anybody i try to change the summed amount on the basis of the newly added product in the cart , i think the issue is not in the commerce_add_to_cart module the issue is in the cart module which is a sub module of the commerce module, since the commerce module is tha parent module of the commerce_add_to_cart module it is taking data like 'total_price' from the OrderTotal and other files of the commerce module, so the issue is not in this module.