1. Mine 18.5K soft clay (search for a script), should take like 24 hrs.
2. Soften it, should take about 18 hrs.
3. Now you should have 2.9 Mill. Bank it all, but 30 gp.
4. Go to Karamja and complete the achievement diary. You can get an onyx now for 258K tokkul instead of 300K tokkul.
5. Go to G/E and buy 28.667 chaos runes.
6. download an auto-seller, make one or sell the chaos by hand in the TzHaar.
7. With 258K tokkul, you can buy an onyx. Go to g/e and sell for 3.4M.
7.1 (Thx loopster) wait to Onyx to be sold (lowest price is advised)
8. Congratulations You just made 500K
9. Repeat step 5-7.
10. Buy party hat and impress your friends