Many pyramids are more sophisticated than the simple model. These recognize that recruiting a large number of others into a scheme can be difficult so a seemingly simpler model is used. In this model each person must recruit two others, but the ease of achieving this is offset because the depth required to recoup any money also increases. The scheme requires a person to recruit two others, who must each recruit two others, who must each recruit two others.
The "eight-ball" model contains a total of fifteen members. Note that unlike in the picture, the triangular setup in the cue game of eight-ball corresponds to an arithmetic progression 1 + 2 + 3 + 4 + 5 = 15. The pyramid scheme in the picture in contrast is a geometric progression 1 + 2 + 4 + 8 = 15.
Prior instances of this scheme have been called the "Airplane Game" and the four tiers labelled as "captain," "co-pilot," "crew," and "passenger" to denote a person's level. Another instance was called the "Original Dinner Party" which labeled the tiers as "dessert," "main course," "side salad," and "appetizer." A person on the "dessert" course is the one at the top of the tree. Another variant, "Treasure Traders," variously used gemology terms such as "polishers," "stone cutters," etc. or gems like "rubies," "sapphires," "diamonds," etc.
Whichever euphemism is used, there are 15 total people in four tiers (1 + 2 + 4 + 8) in the scheme - with the Airplane Game as the example, the person at the top of this tree is the "captain," the two below are "co-pilots," the four below are "crew," and the bottom eight joiners are the "passengers."
The eight passengers must each pay (or "gift") a sum (e.g. $1000) to join the scheme. This sum (e.g. $8000) goes to the captain who leaves, with everyone remaining moving up one tier. There are now two new captains so the group splits in two with each group requiring eight new passengers. A person who joins the scheme as a passenger will not see a return until they advance through the crew and co-pilot tiers and exit the scheme as a captain. Therefore, the participants in the bottom 3 tiers of the pyramid lose their money if the scheme collapses.
If a person is using this model as a scam, the confidence trickster would make the lion's share of the money. They would do this by filling in the first 3 tiers (with 1, 2, and 4 people) with phony names, ensuring they get the first 7 payouts, at 8 times the buy-in sum, without paying a single penny themselves. So if the buy-in were $1000, they would receive $8,000, paid for by the first 8 investors. They would continue to buy in underneath the real investors, and promote and prolong the scheme for as long as possible to allow them to skim even more from it before it collapses.
Although the 'Captain' is the person at the top of the tree, having received the payment from the 8 paying passengers, once he or she leaves the scheme is able to re-enter the pyramid as a 'Passenger' and hopefully recruit enough to reach captain again, thereby earning a second payout.