Rafael Benitez's men broke their long-standing transfer record in January as they paid Atlanta United in the region of £21m ($27m) for playmaker Miguel Almiron, who starred on his full debut against Huddersfield Town on Saturday.
Despite this, Rangnick, discussing Leipzig's interest in Joelinton, is sceptical that Newcastle would shell out a massive fee, as controversial owner Mike Ashley looks to sell the club.
He did acknowledge that the purported asking price of €60m would also rule Leipzig out of the running for the 22-year-old, though.
"I only read that Newcastle want to pay [roughly] £50m for him," Rangnick said of the reports, speaking before Leipzig face Hoffenheim and Joelinton on Monday.
"Coming with this fee, the player would get a fitting contract. We are not able to pay this, whoever the player is.
"If these numbers are true, [Leipzig could not pay it]. Although it would surprise me, because Mike Ashley, who has never paid more than around £20m for a player, is thinking about selling the club and wants to make a profit.
"That he, at the end of his tenure at Newcastle, would buy a player for so much money is hard to believe.
"But it doesn't matter, even if the fee is a bit below that. We will never be a club who can afford such players. It amused me a bit in these past days, reading this and also being linked to the player.
"He is a great player but there are more great players - at Hoffenheim and at other teams in the Bundesliga."
Joelinton has scored 10 goals in all competitions this season, having spent his first two years at Hoffenheim out on loan with Rapid Vienna.
He extended his Hoffenheim contract through to 2022 in November.