If you require Cogs, check the Trading Post before scavenging. I have constructed a Cog Mold at great personal cost, and am offering its use to you at a very reasonable price. Scavenge any other resource for me and I’ll give you 5 cogs, which is 67% more than you would otherwise get.
I also offer the direct use of my Cog Mold to turn Iron into Cogs at a price of 3 Iron per transaction. 10 Iron will get you 6 cogs, twice the amount scavenging gets you!