There is another shop way up on level 55 of the Wilderness, which sells Law Runes for 156 gp and Nature runes for 89 gp each (you need to be a Member to complete this). The average street runescape gold price varies from 600 gp each for Law runes. For Nature Runes the average street price is 300 gp each.

Go to Ardougne. Behind the Castle there is a small house which has a Lever in it. You will be teleported to the Deserted Keep. Exit the Deserted Keep runescape accounts by going North and then go to the west and you will find the Mage Arena where there is a Magic shop just to the North West of the Magic Arena. WATCH OUT! It’s Wilderness 55, and anyone can kill you. Run to the shop, and choose a server with not many people on it! When you pull the Lever of the Second house, you will be teleported to a Cave. Inside that Cave you are SAFE. Nobody can attack you in there.
Also there is a Bank inside, so you don’t need to bring anything of value with you actually on your journey from Ardougne to the Cave. Go to the Man standing in the corner and bank him. Take out your cheap runescape moneyand go trade with Lundail. Sometimes he has law runes, sometimes he doesn’t. But they pop up every 1min so it’s ok. Every 1min buy the law rune,
then wait, and then buy it again. Stay there for about 30mins or longer. Let’s say you have bought 100 Law runes, priced at 320GP each. You sell them for 500-600 each.

BUY: 100 Law runes // 320GP each = 32,000GP
SELL: 100 Law runs // 600GP each = 60,000GP

Profit Margin 28,000GP!

The more you buy the more profit you get of course. --