If you want to make easy cash, simply put an offer on for Oysters on in the GE (as many slots as you can). You must be relatively soon after the GE update if you want to get them.
If you were to buy 500 Oysters, it would cost you 280K. After opening them in the hope of getting Oyster Pearls, you would finish with approximately 650K!!
That's 370K profit, and the entire process would only take about 5-10 minutes of your time, if you use a GE update notifier instead of camping.
Hope you liked this guide
