Solved by Kip DeGraaf

solution: gold chain

Can we get change back from the laborer?

If so, we cut one link to make a chain of 4 links, a chain of 2 links and the cut link itself.

Day 1, we give him the cut link
Day 2, we take back the cut link, give him the 2 link chain
Day 3, we give him the cut link
Day 4, we take back both the cut link and the 2 link chain, give him the 4 link chain
Day 5, we give him the cut link
Day 6, we take back the cut link, give him the 2 link chain
Day 7, we give him the cut link