In Chapter 6 or later, the Combat Scope Betas cost 3,000 gold, one glass
shard, and one scrap of iron to make. The wandering merchant sells glass
shards for 200 gold and iron scraps for 150 gold. Combat Scope Betas
sell for 4,100 gold. Thus, you will make a profit of 750 gold per scope.
The best time to do this is chapter 6-7, before the merchant starts
wandering she is always at the Waterless Bridge. In Chapter 8+, she can
be at Forsaken, the Waterless Bridge, or the Righteous Tower. It is
recommended to get into an enemy counter, run away, and check the
location to see if she is there. Time phase changes also alter her
position. Repeat this trick as many times as desired.