Tickets for the One Love Manchester benefit concert are being listed for auction online at several times their face value.
Stars including Justin Bieber, Katy Perry, Coldplay, Take That and Miley Cyrus will join Ariana Grande at Old Trafford Cricket Ground with the £40 tickets snapped up in less than 20 minutes on Thursday.
Proceeds from the event will go towards the We Love Manchester Emergency Fund to support grieving families and victims of the attack, but it appears people are looking to cash in by selling tickets at inflated prices.
One eBay seller was looking to offload four tickets to the gig for £1,250 - which would net a potential profit of nearly £1,100.
The listing was taken down shortly after being seen by the Press Association.
Meanwhile, more than 10,000 people applied for free tickets to the benefit concert despite not attending the pop star's targeted gig last week.
Ticketmaster set aside tickets for the 14,200 people who were at the Manchester Arena concert, but more than 25,000 people applied to this weekend's event being held to raise funds for the 22 victims of the terror attack.
A spokeswoman for the company said: "Sadly, over 10,000 unscrupulous applications have been made."
Major secondary ticketing sites Seatwave, Get Me In, Viagogo and Stubhub have all pledged to not allow the reselling of tickets on their websites, while eBay said it would immediately remove any listings attempting to profit unfairly from the terror attack.