And in 1984, Cashbox published a very interesting article after gathering information from an EMI's press release at the time. This was specifically included on an issue from March 1984 and included the biggest selling acts on that label up to that date, with Queen obviously included:
BUENOS AIRES — The local EMI branch has released some interesting news about sales figures by artists that are currently in the catalog. The list is headed by the Beatles, which sold more than two million albums or cassettes in Argentina during its career; Spanish chanter Joan Manual Serrat and British group Queen have exceeded 500,000 units; while folk artist Tarrago Ros, Mexican teen star Luis Miguel, all-time tango star Carlos Gardel and Spanish artist Dyango have topped the 200,000 mark. There are eleven artists with more than 100,000 albums sold: Salvatore Adamo, Chilean group Los Reales del Valle, rock artists Deep Purple, Paul McCartney & Wings and Johnny
Rivers; tango leaders Osvaldo Pugliese, Enrique Rodriguez and Osvaldo Pugliese; rock artist Juan Carlos Baglietto, melodic chanter Gianfrance Pagliaro and country & western star Kenny Rogers.
Over 500,000 LPs sold by early 1984 (before the release of The Works) and the second best selling English speaking act for the record company, just behind The Beatles (although this last group had actually sold much more by then).
For all I know, this is how the sales per albums are likely to have been spread:
Queen - 20,000
A Night At The Opera - 50,000
A Day At The Races - 25,000
News Of The World - 45,000 (this one was released in May 1978 and reached 30,000 in early 1979)
Jazz - 45,000
Live Killers 40,000
The Game - 150,000 (certified 2x platinum for 120,000 shipped in February 1981, when the band visited the country)
Flash Gordon - 30,000
Greatest Hits - 60,000
Hot Space - 30,000
No information on Queen II or Sheer Heart Attack, but these two would push the tally to over 500,000 units. Both likely to have sold around 15,000 copies by that time.
Believe it or not, by April 1978 Queen had only sold 30,000 units with three of their albums. Almost six years later, that number increased to 500,000, meaning they sold an average of 80,000 pieces a year during that period.
News Of The World, Jazz and especially The Game really helped them. Those sold very well but also generated very good catalogue sales. in 1978 and 1979, for example, A Night At The Opera was selling 1,000 units a month, better than most catalogue albums at the time.