Magento : issue in shopping cart

Question

first I'm developping an extension for custom price so when i add a product to cart with 400$ and add again the same product with 500$ it gives me in total 1000$ like described in image bellow :

so this is not logic an d the total must be 900$ now i wanna solve that problem but i don't know where to start I've been confused i wanna do like this :

Answer 1

May i know the products are different. if the products having same sku it will take only one price.

For this u need to add two products with same name and different "SKU". I think it will work..