Being a reformed Baptist, FK, you must believe that whatever happened, including the Fall, was in God's design and that God controlled the events as they unfolded. He wrote the script, and He choregraphed it. He was not driven to do either. It was by His choice that man sinned. Did man really have a choice to change God's plan?
"Did man really have a choice to change God's plan?"
How can the created change the plans of the Creator unless it was defective and the Creator did not know this? All that was created and all that occurs was planned before the foundation of the world for the glory, praise, and good pleasure of the Creator.
I agree with everything BD said. Everything that has been created and everything that has happened has been under God's explicit and sovereign design. Man has no power to change God's plan. However, I'm not exactly sure how this relates to whether God demanded a price. The price that God did demand we could never meet. That only leaves one option, if some men are going to be saved, as far as I can see it.