Ticketmaster is catching some fan heat on the other side of the world, as Celene Dion fans are roasting the vendor for the immediate sellout of a concert last week, with tickets appearing for resale on the company’s platform immediately.

“I want to know how Ticketmaster can allow this to happen,” one fan asked, according to TVNZ.com.nz.

Marked as ‘in trade’ on Ticketmaster’s website, the tickets reportedly come from promoters, event sponsors, or advertisers related to the concert – rather than a one-off individual reselling extra tickets they purchased, per TVNZ.com.nz. Ticketmaster, citing confidentiality and privacy policies, declined to comment on who was selling the tickets, which were marked up by a minimum of $400 over the face value.

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“Our priority is to help artists get as many tickets as possible into the hands of fans,” it responded in a statement.

It is well known that a huge number of tickets are gone before they ever get to a general sale for just about any concert or event of note. In 2016, findings by New York Attorney General Eric Schneiderman indicated that as much as 90% of tickets are held back for venue or artist insiders, presales, or potential production issues that would prevent a fan from enjoying the show from a particular seat. In this particular instance, the tour is being promoted by Frontier Touring and ConcertsWest/AEG Presents, not Ticketmaster parent Live Nation.

Recently, in reaction to the outcry over Elton John tickets flying off the shelves in similarly immediate fashion, former Live Nation executive and veteran promoter Michael Cohl pointed out that the simple laws of supply and demand are responsible for such situations.

“By the time [fan club presales, VIPs, “friends and family” and other holdbacks are] all done, if you’re limited to four tickets per purchase, it’s approximately 6,500 people that will get tickets,” he said. “You’re only going to have 6,000 to 9,000 ticket buyers (who get through) and you could have 300,000 trying … So the idea that people will just immediately say, ‘Well, it sold out in a minute and a half and it’s cheating’ — that’s total crap. Of course, it had to sell out instantly. Supply and demand — period. That is never going to change.”

In the instance of Dion, her stops in Australia are the first for her in over a decade, while the two stops in New Zealand were the first in over 20 years. So demand was at a peak for the back-to-back nights at Auckland’s Spark Arena on August 11-12.

While it’s easy to pitch blame at Ticketmaster or secondary sellers, it’s likely that Celene Dion fans just wound up suffering from a simple math problem: Very high demand, very low supply.