Clone, no that's rubbish and them wanting chargeable time via a new install and long term when you have the inevitable maintenance nightmare it would produce. There are many ways to do it as various factors such as product count, customer groups, configurable products come in to play. The more you have the simpler the solution you need or the larger the hosting environment. Magento loads datasets in to memory so if you have complex or high volume pricing structures your environment will stop functioning and you will lose conversions.
You also have options like MAP and extensions, but you want to take a copy of the site into a sandbox and test from there. As an example, you could use MAP for prices to be shown only in the cart and password protect the cart for login, it's not elegant but it's business functional and almost instant to implement using internally tested Magento functionality (that one comes from a partner).
You will have to go through all the combinations to find the correct solution for your company, It will be the full learning curve, a good consultant would be able to do that for you but they are few and far between. Cloning, some of the stupid things we have come across along with our partners informing us (listed on Bloomberg so Magento is the bottom of the food chain to them) you just wonder how online companies ever succeed, with a healthy amount coming from 'certified' Magento partners.
