Loot Hoarding

Note that all the guns in the personal locker are in top condition. As you reach Pripyat, the military mechanic repairs all damaged weapons and equipment for free, even if it's not even sellable to dealers. Originally meant to ease player's travel through Pripyat, however it is possible to have Degtyarev (the player character) and said mechanic cooperating in order to ruin the gun trade in the Zone via market inflation.
Bonus points: In freeplay, military leaves the Zone... but their base gets occupied by Loners instead, and roles of mechanic and medic are taken by Uncle Yar, who as well repairs all stuff for free. Meaning, you can continue to run damaged guns to Pripyat for repairs then back for selling.