Question: Who has sold the most concert tickets ever?
Disambiguated questions and answers: question: Who has sold the most concert tickets ever in a single concert as of July 1, 2017?
Who has sold the most concert tickets ever in a single concert as of June 28, 2005?
Who has sold the most concert tickets ever in a single concert as of July 31, 1999?
answer: Il Blasco
Vasco
Vasco Rossi
Bijelo Dugme
Glay
Natural Questions answer: U2 (from the Wikipedia article "List of highest-grossing concert tours")