If you are on pc and are two people in the game you make one of the persons drop his equipment or other items of high value, then the second player picks them up and leaves the game, then the player who dropped the items alt + f4. if done correctly your items should now be multiplied

this can be done on all pkatfirms, and the player acquiring the gear or $$ diesnt have to leave the game .. just the original owner.

you also failed to mention that there should be little movement so autosave doesnt get hit by accident.

how can you do it by yourself?

get a Bee shield and farm bosses (bunker, warrior, etc). Its not unlimited, but it goes up pretty fast >__>