The only reason it's there is so you know how much to award on the chronicle sheet. Say they fail to retrieve the box. Not do they risk failing the overall mission (you only have to complete three out of four, in the case of First Steps 1), but even if they succeed they don't get full gold on the chronicle.
But for me, I had XXX throw each character a sack of gold, saying "Here's a little extra for your trouble." It was available for them to spend if they needed more equipment, but it didn't change the amount of gold they received on the chronicle.