"For his age, he is very advanced - a top player that many teams wanted," Kroos told podcast Einfach mal Luppen.
"If Real Madrid put down that much money, and I have a lot of confidence in that, it's a very good transfer."
Criticism of Benzema
"You can do it or leave it, it's an individual decision for everyone," Kroos said of Benzema's transfer.
"I would have thought he would have pursued the idea of ending his career in Madrid. At the end of the day, in football, there is an end."
Benzema has signed a three-year contract with Saudi champions Al-Ittihad. "I would (suggest) that he didn't know the club two weeks before (joining)," said Kroos, who also spoke highly of the Frenchman.
"There have been few strikers in the last 15 years who could handle the ball (like him). It was a great pleasure to play with him," he concluded.
Hazard sets an example
"Welcome to Madrid," said Kroos, who admitted he hadn't seen 'an incredible number of Dortmund games' recently.
However, Kroos also issued a warning, and took the opportunity to lash out at an ex-colleague in the form of Hazard.
The Belgian had switched from Chelsea to Real in 2019, in a big-money move, but failed to even nearly hit expectations.
"We also had someone who came for a lot of money and practically let his career die out," said Kroos of Hazard, with reference to Bellingham's deal.
"A lot of money - and I think everyone would say in retrospect (it) wasn't such a good transfer."