I actually consider it more of an art than a science, but this is a nice synopsis on how ticket pricing drives scalpers:

Most concertgoers don’t usually consider ticket prices as incredibly low. After barely keeping up with inflation for decades, concert prices have risen wildly since 1996, or around the time when baby boomers, who helped start the industry, aged into a lot more disposable income. (It was also around this time that Internet piracy made the music industry more reliant on concert revenues.) These days, prices can seem incredibly high. Barbra Streisand, who charged more than $1,000 for some seats at a concert in Rome, inspired so much anger that she canceled the show. Yet to an economist, the very existence of scalpers and companies like StubHub proves that tickets are far too cheap to balance supply and demand. Pascal Courty, an economist at the University of Victoria, in Canada, who has spent the better part of 20 years studying the secondary-ticket market, has identified two distinct pricing styles. Some artists, like Streisand and Michael Bolton, seem to charge as much as the market will bear — better seats generally cost a lot more; shows in larger cities, with higher demand, are far more expensive, too. (If you want to catch Bolton on the cheap, head to Western New York.) The second group comprises notable acts, like Bruce Springsteen and Pearl Jam, that usually keep prices far below market value and offer only a few price points. An orchestra seat to see the Boss in Jersey costs only about $50 more than the nosebleeds in Albany.

Springsteen’s style might seem more altruistic, but performers who undercharge their fans can paradoxically reap higher profits than those who maximize each ticket price. It’s a strategy similar to the one employed by ventures like casinos and cruise ships, which take a hit on admission prices but make their money once the customers are inside. Concert promoters can overcharge on everything from beer sales to T-shirts, and the benefits of low-priced tickets can accrue significantly over the years as loyal fans return. In part, this explains why artists like Springsteen and Petty are content to undercharge at the gate while others, perhaps wary of their own staying power, are eager to capitalize while they can.

Regrettably, I once bought a ticket to a Red Sox game from a scalper that turned out to be a fake. These days I usually buy direct from source. I’ve had good luck with StubHub as well.