PSG smashed the previous world record fee paid by Manchester United for Paul Pogba last year after agreeing to stump up €222 million to free the Brazil star from his Barca contract.
And Liverpool boss Klopp believes it is now conceivable a club could pay Messi's even more ludicrous release fee to prise the five-time Ballon d'Or winner away from Camp Nou.
"It’s pretty simple. Until now it was simply seen as impossible," Klopp told DAZN. "Then there is the list, with the release-clauses for Barcelona. Leo Messi, €300m.
"In a period of just a month that suddenly sounds possible too. That used to be an outrageous amount. They just set that amount randomly. I mean who would pay €300m. And now it simply happened."
New controls on the transfer market have been suggested in the wake of the Neymar deal, with Barcelona and LaLiga both threatening to report PSG over Financial Fair Play rules.
"I don't even know if this is right," Klopp said. "No coach would demand such a thing. That's been decided on other levels and now he is a PSG player, obviously. A simple solution would be a rule. Where we want to go and where this should stop.
"The biggest clubs can decide on that, where they would want to set a limit. €150m or €550m or whatever and then no one would complain anymore. This is a topic now since it happened for the first time."
PSG's capture of Neymar is intended to turn the Ligue 1 side, who finished second behind Monaco in Ligue 1 last season, into genuine contenders to win the Champions League, but Klopp stressed there is more to the sport than signing star players.
"I love football, because you make each other stronger," the German added. "You can develop a team. A star player on one side and another one on the other makes the player in the middle a star too.
"That's what I like about this sport. These hero stories - that one is better than everyone and so on - I don't think that Neymar had that specific idea. They made the offer and they finalised it."