Question:

Why does my separation agreement say “in consideration of the sum of ONE DOLLAR ($1.00), to each of the parties in hand paid by the other, the receipt whereof is hereby acknowledged”?

Answer:

Mere promises are not enforceable by the court.  The court requires something more to have an enforceable contract.  Each party must give something of value to the other.  That is called consideration.

The consideration may be nominal.  “A rose, a hawk, or a peppercorn will suffice.”   Williston on Contracts.

Modern lawyers, many of whom may not even know what a peppercorn is or where to find one, have found it more convenient to make one dollar the separation agreement consideration.