Jurgen Klopp has shrugged off criticism of Liverpool's transfer business after he has been accused of hypocrisy with the Anfield club splashing the cash recently.
Klopp's side this summer paid a world-record fee for a goalkeeper to sign Alisson from Roma in a deal worth up to £65million, while in January Virgil van Dijk became the most expensive defender in football when he arrived at Anfield for £75m.
But two years ago, while Manchester United were set to spend a then record fee of £89m on Paul Pogba, Klopp had suggested he would quit the game if those large fees became the norm rather than the exception.
"We don't care what the world around us is thinking," Klopp said.
"Like Manchester United didn't care what I said.
"It is only an opinion in that moment. Did I change my opinion? Yes. That is true. But it is better to change your opinion than never have one.
"Whatever people say and bring it up again and again, I have had worse days in my life and worse things happen to me. We have the players we wanted. I am fine with that."
Alisson's arrival follows the signing of fellow Brazilian Fabinho from Monaco, while midfielder Naby Keita has joined from RB Leipzig and Xherdan Shaqiri from Stoke.
Klopp added: "The world has changed completely.
"Better players than we already have are not waiting around the corner. You can't get the world-class goalkeeper who had a really long contract at Roma on a free transfer.
"It is not for me to say we don't want to pay big money because in the end Liverpool is not successful. That doesn't work."
Klopp also said that Mohamed Salah has come back from the World Cup with no problems.
The Egypt forward, who scored 44 goals in all competitions for the Reds last season, suffered a dislocated shoulder in his side's Champions League final defeat to Real Madrid.
He recovered to play two games at the World Cup for his country, who lost all three of their group games in Russia.
Klopp said: "He has fully recovered. We were constantly in contact (during the World Cup) and he was fine. Shoulder-wise, he had no problems.
"He looks full of joy and is really happy to be back. It was nice to see him yesterday for the first time, the same for Sadio (Mane). They look very fit."
Cameroon international Joel Matip is ready to fight for his Liverpool place this season as he believes Klopp is assembling an expensive squad capable of challenging for major honours.
The defender has returned to action having been forced to miss the final weeks of last season with a thigh injury.
In that time, Matip had to watch as Liverpool reached the Champions League final without him, and saw Dejan Lovren and Virgil van Dijk establish themselves as the Reds' first-choice centre-back pairing.
Lovren's World Cup exploits, however, will give the 26-year-old a chance to reassert his claims in the coming weeks.
The Croatian is not due back with the squad until August 6, and so unlikely to be considered for Liverpool's opening Premier League game with West Ham just six days later.
It means Matip will have to battle Joe Gomez and Ragnar Klavan for the right to partner Van Dijk - and the former Schalke man is up for the challenge.
"Of course there is competition," he said, speaking to Goal.com. "We had the quality before and now we have a lot of self confidence.
"But I also have no doubt of my quality!
"And with a team like ours, there are always so many games, so you try to get the chance."
Matip added: "I'm on a good way, of course.
"The fitness is not at 100 per cent but I'm not the only player who needs this time. But this is preparation to get a good fitness level, I'm on a good way and feel self-confident. I still need some time."
Matip admits it was difficult to watch from the sidelines as Liverpool went all the way to Kiev back in May, losing in heart-breaking circumstances to Real Madrid.
"Nobody wants to see games like this from the stand as a player," he said. "But you still try to fight and to do what you can from the bench or the stand. It is what it is."