Riot Fest is underway in Douglass Park on the West Side of Chicago. The thousands of people attending this year paid a lot more for tickets than they did back when it started in 2005.

The Federal Trade Commission and seven states - including Illinois - are suing Ticketmaster and its parent company, Live Nation, over their resale practices, accusing them of deceptive pricing.

Fans at Riot Fest said seeing their favorite musicians throughout the year has become an investment, and when using websites like Ticketmaster, they expect to pay more

Blink 182 headlined Friday's performers at Riot Fest, with tens of thousands expected to pack Douglass Park.

"It's a very, like, chill crowd. It's very welcoming," said Riot Fest fan Chris Zarek.

But what's not as welcoming are ticket prices for concerts, shows, or a game on resale marketplaces like Ticketmaster.

"I shouldn't have to pay an arm and a leg for my favorite artists," Daniel Garcia said.

The FTC and seven states, including Illinois, sued Ticketmaster Live Nation on Thursday, accusing the event services of allowing brokers to scoop up event tickets and resell them at inflated prices, costing consumers billions of dollars.

In a legal complaint filed in the U.S. District Court for the Central District of California, the regulatory agency also alleged that Live Nation, which owns Ticketmaster, used "bait-and-switch pricing" tactics by advertising lower ticket prices than what was actually available to customers, and by selling millions of tickets to brokers -- often at a significant markup -- despite limits that artists had placed on such sales.

"Fee after fee after fee. I'm saying what is this, man? I'm like, I thought my ticket was like 80 bucks. Now it came out to like $105 total, and that's ridiculous," Garcia said.

While artists set prices and limits for how many tickets fans can buy, the lawsuit accuses Ticketmaster of knowingly allowing ticket brokers to exceed these limits.

Fans have accused Ticketmaster of using what's known as dynamic pricing or surge pricing to increase or drop ticket prices in real time based on demand.

Chicago ticket broker Steve Buzil said part of the pricing problem is the limited number of tickets that are actually released to the public in the primary market.

"The harder they make it for people like to get tickets, or anybody, the higher the price is going to be in the marketplace. So they know what they are doing. It's very self-serving

Single-day tickets for Riot Fest cost $130 through the official website. That same ticket on Ticketmaster is selling for more than $270.

"We spend a lot of money going to concerts and we try to not let money avert from our fun, but it has for sure this summer," Jessica Griffin said.

Ticketmaster and Live Nation did not respond to requests for comment.

Riot Fest fans lament growing concert ticket prices as feds sue Ticketmaster for deceptive practices