A 1.00 L sample of saturated Ag_{3}PO_{4} solution is allowed to evaporate at 25 degrees Celsius to a final volume of 500 mL. What is [Ag^{+}] in the solution? Justify your answer.

I thought the [Ag^{+}] would be doubled since the moles per liter of Ag_{3}PO_{4} would have increased and therefore producing more of its products. However, I was told the answer was that the [Ag^{+}] would remain the same in a saturated solution of Ag_{3}PO_{4} since it is independent of the volume of the solution. I don't get this. Can someone please help me out? Thank you.