Thats a nice explanation.

May I know what kind of services are available in the market for ready integration? What the cost involved to use those solutions? What are the various factors we have to consider while picking up a solution apart from cost?

There are several free, premium CMS (Content Management System) available in the market. But there is a good powerful and above of all fully free available. It is oscommerce.

http://www.oscommerce.com

Most of the Web Hosting Companies now a days provide a Auto Installer or one click Installation service called Fantastico which installs oscommerce and other shopping cart cms in just a click. Life has become easy I guess!

Here's a good resource for those who values their time: Shopping Cart Reviews. You can check & compare them all

My preference is also PHP. It's just so widespread now... And it's became very powerful, too. So I'm using a PHP-based shopping cart called Avactis.

You can develop php shopping cart software which is the best technology & easy to develop.There are many open source php shopping cart is available on the net.You can refer zeuscart - Shopping Cart Software which is developed in php and it supports more features.