By the time tickets went on sale for rapper Jay-Z’s much-hyped concert at the new Barclays Center last fall, some 62 percent of the tickets had already been snapped up, according to data from SeatGeek.

The online ticket search firm found that secondary ticket sites were flooded the day after American Express held a pre-sale on July 11.

Some 6,700 tickets were available for resale on July 12. The Barclays Center’s official seating capacity for the shows is 14,586.

Reselling a ticket isn’t illegal, but for hot acts those tickets come at a much higher premium.

Some in the industry argue the secondary market is the best way to judge the initial ticket’s value. Those that command big premiums in the secondary market clearly were underpriced.

SeatGeek, however, notes that some individuals offer tickets for sale without owning a ticket, which may inflate secondary market totals.

SeatGeek estimates that up to 30 percent of the entire Jay-Z ticket allocation was sold via American Express pre-sale.

Will Flaherty, a spokesman for SeatGeek, said that figure is consistent with what happens at most venues where credit card companies hold back tickets for their customers.

He suggests fans get savvy in their search for tickets.

“Sign up for fan clubs, they may send you an alert,” he said. “If an artist is coming to your city, check all the sources for tickets: an artist’s website. Does the credit card grant you access?

“Ticketmaster shouldn’t be the first place you check.”