Tickets for the final Avengers film are being sold on eBay for over $10,000 (£7,636), just days after being listed for $1,000 (£763).
One of the selling service's user is offering four tickets to an opening night screening in Chicago for $5,500 (£3,803).
Others can flog tickets for $200 (£152) and $500 (£380).
For those in the UK who failed to secure tickets for the opening night on 25 April – one day before its US release – a single ticket is on offer for £380.
According to Fandango, the Marvel sequel has achieved more first-day pre-sales through the company than any other film, beating the previous chart-topper Star Wars: The Force Awakens.
In fact, the rush of fans attempting to buy tickets caused the website to crash, with fans claiming they had to wait more than an hour to buy tickets.
Many other ticketing systems in the US faced similar problems, including AMC Theatres, Regal Cinemas, and Atom Tickets.
The former has announced it will show all 22 films in the Marvel Cinematic Universe as part of one giant marathon.
