Basically want to options, here is an example.
I have a product listed, which is a psd poster template. On the page I have 2 add to cart buttons;
1) Buy Non-Exclusive £10
2) Buy Exclusive £100
If the user adds to cart via the non-exclusive button it just adds normally (setup to have unlimited stock) and the item continues to be available to everyone.
If they add to cart via the exclusive button it adds to the cart with the different price and changes the stock to 0 so nobody else can purchase.
Hope you understand!
Simon