How much does a good E-Commerce Website cost which can handle more than 1000 products and a lots of hits?

These days listing thousands of products on your E-Commerce website is no big deal. There are many E-Commerce frameworks that can easily handle at least 1000 products without any slowdowns. Magento is one such E-Commerce framework. In fact Magento is considered the most comprehensive E-Commerce platforms.
Listing a thousand products means that you will be having many product categories and Layered Navigation (product filtering) will be required. Magento provides indexing for all its categories and has some of the most advanced Layered Navigation Extensions available.
As far as performance is concerned, Magento has just too many features to implement optimized performance. It has Compilation to combine a magento's module into a single file. Image cache to resize images only once. And browser cache is easy to implement , so, the if the website has been visited once, it will load faster the next time a user visits it. Apart from all this it has something called Full Page Cache which saves the pages of all products in advance so the server does not have to generate the page on every the page is visited. Full Page Cache makes your website literally blazing fast.
And as far as uploading of products is considered. Bulk products upload is very much possible in Magento. You can create CSV files in Microsoft Excel  with all the product details and product images can be uploaded together with product codes as file names.
Though you have many other E-Commerce framework options available but Magento will be your best bet as per your requirements.