The La Liga champions won the race to sign the prodigious Brazilian last week after having reportedly agreed to meet his stunning €45m (£38.8m) release clause.
Liverpool and Bayern Munich were also credited with interest in the youngster, who made just one appearance for Flamengo before becoming the most expensive teenager in world football.
The staggering transfer fee has raised eyebrows across Europe but Vinicius' representatives insist Real were not the only club who were ready to pay the huge fee.
Frederico Pena, Vinicius' representative, told Globoesporte: "If anyone receives criticism, it will be Real Madrid for the bet they have made," AS reported. "For them, they are assured it will work. There were other clubs interested and one offers more money."
Pushed on who made the bigger bid, Pena added: "Barcelona put together a more lucrative package for the player. Many believe that it is madness but they were not the only ones involved in the supposed madness. They are not the only crazy ones will to pay for the quality of Vinicius."
Pena dealt another embarrassing blow for Barcelona in revealing his client "liked the project" at Real Madrid more than the one presented by the Catalan giants. "People get the impression that he made the decision based on a financial situation but it is not the truth. I assure, the negotiation stance Real Madrid took was better."
Fifa regulations do not allow international transfers for players under the age of 18, meaning Vinicius will not be able to link up with Los Blancos until July 2018, remaining at Flamengo until then. In a statement, Real have suggested the attacker could remain at the Brazilian club until 2019 to continue his development, although a move to Madrid could take place earlier than that if both sides can come to an agreement.