Liverpool lost out to Premier League rivals Chelsea, who completed deals for British record signing Moises Caicedo and fellow central midfielder Romeo Lavia, who were both targets for Klopp's side.
Klopp also lost two of his midfield stalwarts in Fabinho and skipper Jordan Henderson to Saudi Arabian clubs in the close season.
"I'm not sure if it's something to do with Liverpool finding it harder to attract (players).
"Everything is more difficult... There are a lot of things that are different this year since last year as well already," Klopp told reporters on Friday.
"Some clubs have a different way to do it and nobody understands 100% how it works, but somehow so far it works. As a normal club, it's really difficult to catch up with them... I don't blame anybody. It's just how it is.
"Saudi Arabia, on top of that, made things not easier. Our window ends August 31st (September 1st). The window there is still open so (if there are) players that aren't happy, then they will come again with even bigger offers."
Klopp said two weeks ago nobody would have guessed Neymar would move to Saudi Arabia where he has joined Al Hilal, highlighting how the league is trying to grow and compete with the popularity of Europe's top leagues.
"It's not written in stone that everyone has to watch the Premier League, or LaLiga or Bundesliga. It's absolutely fine if they try to grow the league. We don't have the right to say that's not allowed," he added.
"China tried it, USA is trying, so it's absolutely fine... But the endless money causes a problem. It will be cool if somebody could find a solution, a little bit regulation.
"So yes, it became more difficult. But not to convince players to go to Liverpool, 100% if I called a million players, they all would have come immediately. You have to make sure you go for the right ones."
Liverpool play Bournemouth on Saturday, a club they beat 9-0 when they visited Anfield last year, but Klopp does not expect the south-coast side to roll over after hiring Andoni Iraola as their new manager.
"If you do research on him it's no coincidence that Bournemouth brought him in. He has an unconventional way. I used to like the phrase 'organised chaos' but I don't know if he likes that," Klopp said.
"They will press properly and have an offensive approach. If we let them play, they will play."
