Obviously, as far as we are concerned, only sales of the original are eligible. While both studio / live versions released in 1978/79 were always treated as the same album, albums Starmania 88, Tycoon, Les Enfoirés Chantent Starmania and Live Mogador 94 are all different albums with different singers.
Thanks to sales of the 20th Anniversary edition in late 1998 plus additional copies up to the end of 2001, the original was up to 1,85 million units by that date. At that point, one more WEA audit certified the original album Diamond for the second time, this one for sales since June 1991, plus 2xGold for the 1979 Live album. Of course, two Diamond awards add for more than 1,85 million but sales from late 1991 to 1993 were part of both awards thus being double counted.
Since 2002 the record continued to sell well. Never featuring the highest rankings, it is still constantly featuring inside the Top 100 catalog chart, having been on it for over 300 weeks since 2002. This performance is particularly good since all versions finally got properly separated since the start of the decade, meaning it was charting on the back of the original only. In 2009, a TV special celebrating the 30th anniversary of the musical, presented by France Gall, boosted strongly its sales. The original was three weeks #1 of the catalog chart, each of them with the Live 1979 #2 and Starmania 88 top 10. In total, the original album sold an estimated 225,000 units from 2002 to 2015.
Net shipment as of the end of 2015 is estimated at 2,075,000 copies.
As usual, feel free to comment and / or ask a question!
Sources: SNEP, Nielsen, IFOP, Platine, Billboard, RFI Musique.