Nonsense. The commissioners were sent to "for the purpose of negotiating friendly relations between that government and the Confederate States of America, and for the settlement of all questions of disagreement between the two governments upon principles of right, justice, equity, and good faith." Nothing specific about NEGOTIATING a transfer, just a vague offer to settle questions of disagreement. Since the south had already seized, or planned to seize, all the federal property in the rebellious states what incentive was there for them to pay for it?
The incentive is in Jefferson Davis's Inaugaral Speech....
The South wanted to leave peacefully, and to be left ALONE.
LIncoln chose war. Not the South, their honor would allow them no other recourse.