Tickets for Floyd Mayweather and Conor McGregor's fight are being resold on third-party websites for up to £44,500.
Fight tickets went on sale at 6pm UK time on Monday, but the first batch of tickets quickly became unavailable just minutes after being released on Ticketmaster.
The cheapest ticket for the event on the website started at £385, while a premium front row seat retailed at £7706, but those prices were far cheaper than the charges on second-hand websites such as Viagogo, Stubhub and Vivid Seats.
Prices on Viagogo range between £2,150 and £44,500, while Stubhub's cheapest ticket is £1,498, with the most expensive costing £34,459. Vivid Seats' tickets are priced between £1,413 and £18,273.
On Tuesday, a floor seat ticket costing £11,065 was sold on Viagogo.
The fighters will square off, in one of the most lucrative matches in boxing history, on August 26 at the 20,000-capacity T-Mobile Arena in Las Vegas.
Tickets were only available to those who had signed up to Ticketmaster's 'verified fans' scheme, and only two tickets could be purchased at a time by any one buyer, in an attempt to thwart tickets being sold completely to touts. However, codes for the right to access tickets were sold for $200 (£153) on eBay prior to the sale.
A spokesperson for Ticketmaster declined to confirm how many tickets would be sold on its platform on Monday but if any tickets remain they are expected to be made available to the general public.
Mayweather, 40, will make his return to the ring following two years in retirement to face McGregor, in the 29-year-old Irishman's first professional boxing bout.
McGregor is the reigning UFC lightweight world champion and in November 2016, he became the first dual-weight UFC world champion in the history of the competition.
Mayweather heads into the contest undefeated with a professional record of 49-0, while McGregor has never been knocked out in his career either but has lost via submission on three occasions, the most recent of which was against Nate Diaz in March 2016.