I train slayer , but forget what critter has RuneScape Gold the best drop of nat. . I'm aware that roaches will drop nats,but unless your into fighting regularly, relying on this to produce nats is extremely slow. Plus, the prices are extremely cheap on certain items and runes can be cheap to purchase if one has enough gp for a mighty stack.
I've only played since 08 and i'm assuming these are the best prices i have seen prices go. In the past i sold runes, but now I am burning them because it's not a major loss in money to make use of the runes i've got. At this time anyway - however, things change... And how to make money fast on osrs i really look forward to this new dumb update that is yet to be discovered in our realm. Then i'm off get some gold from the monster's butt.