Which technology is used for your site? If it’s made using any of the open source technologies or CMS systems, it would not have costed that much. For example using WordPress or Magento for developing an eCommerce site gives you freedom to use tons of plug ins to add desired functionalities but on the flip side, if these functionalities are created by developers themselves, it would of course cost a lot. Now, You can ask to developer to fix the problems which you are getting on the page.