Joel Embiid #21 of the Philadelphia 76ers reacts in front of Chris Silva #30 of the Miami Heat in the third quarter at the Wells Fargo Center on November 23, 2019 in Philadelphia, Pennsylvania.

It wasn't long ago the Philadelphia 76ers sat at the bottom of the NBA's attendance rankings.

But after six years of rebuilding, the Sixers have returned to the top of the league's attendance records and recently reported their 100th consecutive sellout game before beating the Miami Heat 113-86 at the Wells Fargo Center on Saturday.

The sellout streak certainly supports an increase in demand for Sixers' tickets compared with previous seasons when the team was in the basement of the NBA standings.

Sixers president Chris Heck said the team only sold 3,500 season tickets in the 2013-14 season, "and the majority of the holders were brokers," he said in an interview. The Sixers finished 17th on ESPN's NBA attendance ranking that season and dropped to 30th in the 2015 season. The average ticket price was roughly $95, compared with an average ticket price across the league that season of $144, according to data provided to CNBC by Ticketmaster.

But one season after advancing to the Eastern Conference semifinals, Ticketmaster says it has seen demand surge for Sixers' tickets, with sales spiking 91% through the first seven home games and average ticket prices rising 28%. The average ticket price for Sixers' contests this season is $131, while the average ticket price for the league is $107, Ticketmaster said.

Of course, having a team worthy of watching always helps. Led by All-Star players Joel Embiid, Ben Simmons and new addition Al Horford, who signed a four-year, $109 million deal over the summer, the Sixers are one of the teams favored to advance to the NBA Finals in June.

But Heck also credited Sixers CEO Scott O'Neil with the increase in demand. He recalled the plan in 2014 to change their operation to focus on the "business side" and rebuilt the team's brand, which O'Neil felt was outdated.

"We got a chance to wipe the dust off it and shine it up," Heck said. "That was the focus for the last six years and continues to be the focus."

Heck said team officials solicited input from fans at townhall meetings. For games that weren't old out, the Sixers would allow some fans to move to better seats. The team also partnered with companies like Dunkin' Donuts, owned by Dunkin' Brands, to advertise its logo.

"Everywhere you turned," Heck said, "it was Philadelphia 76ers. So, what happened is, we gained the confidence of the fan that has always been the Philadelphia sports fans, and we also started a new wave, also a cult following, of fans under the age of 35."

As the Sixers prepare to host the Sacramento Kings before Thanksgiving, the team says it has 14,000 season-ticket holders and more than 10,000 fans on the team's official waiting list, Club 76. The team finished first in home attendance last season, averaging 20,441 fans per game. After seven games so far this season, it's again ranked No. 1 with an average of 20,508 fans packing the arena each game.

The Sixers also announced a sponsorship with online sports betting provider Fox Bet on Monday, marking the first partnership of its kind in the NBA.

Owned by Fox Corp., Fox Sports joined technology-based product provider The Stars Group to create Fox Bet, which launched in September. Under the agreement with the Sixers, Fox Bet is expected will advertise on the team's traditional, digital and social media platforms, including throughout the Wells Fargo Center on game days.

The Sixers ownership group is led by billionaire Josh Harris, who co-founded private equity firm Apollo Global Management. Harris purchased the team in 2011 for roughly $290 million. According to Forbes, the Sixers are currently worth $1.65 billion, earning $268 million in annual revenue.