Actually its very clearly stated that if they realize they can't pay the cost, they should ask for terms of peace.
Literally, in the parable, terms of peace means they realize they don't have the strength to give up all their possessions and they ask God to do the impossible, give them that strength.
James 1:5-11
5But if any of you lacks wisdom, let him ask of God, who gives to all generously and without reproach, and it will be given to him.
6But he must ask in faith without any doubting, for the one who doubts is like the surf of the sea, driven and tossed by the wind.
7For that man ought not to expect that he will receive anything from the Lord,
8being a double-minded man, unstable in all his ways.
9But the brother of humble circumstances is to glory in his high position;
10and the rich man
is to gloryin his humiliation, because like flowering grass he will pass away.
11For the sun rises with a scorching wind and withers the grass; and its flower falls off and the beauty of its appearance is destroyed; so too the rich man in the midst of his pursuits will fade away.