I don't think much has changed in the way of the economy in Minecraft or real life. Find items which people want a lot of whether that be concrete or quartz or diamonds and supply huge amounts cheaper than others. This may get you quick money or it may take ages it's all random how people will react. Look at the auction house to see what people tend to buy For some items to sell: Concrete, Obsidian, Quartz
Another thing that is in relatively high demand and goes for a lot is logs, if you can sell big quantities of wood logs you can make a pretty good amount of rupees.
Wood, Sand, Gravel, Glass, Sandstone, Terracotta Check what the big malls need. Also sell through auctions.
Yeah, that's why you can get a lot of money. You should probably have some reliable way of getting heads, though.
Yes it is and the drop rate is around 8% with looting. But I was more referring to Sach's source of wealth he didn't mention in his post.