All aspects of the Buy bet are the same as the Place bet except: 1) A Buy bet pays off at true odds, 2) You have to pay a tax, or a vigorish, to get the true odds, and 3) A Buy bet is positioned on the layout differently. Everything else about the Buy bet is the same as the Place bet.
The casino is in business to make money, so they’re not going to give you true odds for nothing (except, of course, the free true Odds bet that you can add to your Pass Line bet–they’re “free” because you don’t have to pay a vigorish). So, how does the casino grandpashabet make money if they pay off a Buy bet at true odds (i.e., true odds means there’s no built-in house advantage)? Ready to get screwed again? They tax you! You believe that? A tax! You have to pay for the privilege of getting true odds. This tax is called a “vigorish” or “vig.”
John Winn is the father of modern craps. His version of the game allowed gambling halls to offer more player-friendly bets in return for a 5% charge. The worst the gambling halls could do was break even on true odds bets, but they still made money because of the added 5% tax. The added charge brought in so much money that they soon referred to it as giving vigor to their profits; hence, the term “vigorish.” The vig today remains at 5%.
Buy bets on the 4 and 10 are always better than Placing the 4 and 10. Buy bets on the 5 and 9 may be better than Placing the 5 and 9, depending on when you pay the vig. However, Place bets on the 6 and 8 are always better than Buying the 6 and 8.
What makes the Buy bet on the 4 and 10 better than a Place bet on the 4 and 10? Suppose you make a $10 Place bet on the 4
where the Place odds are 9:5, which means you win $18 for your $10 bet ($10 divided by 5 = $2, multiplied by 9 = $18). Now, instead of a Place bet, suppose you make a $10 Buy bet and pay a $1 vig for the privilege of getting true odds, which are 2:1. For a $10 Buy bet on the 4, you win $20 but have to pay the $1 vig, which results in a net payoff of $19. Comparing results of the two bets, the winning Place bet nets you $18; whereas, the winning Buy bet nets you $19.