As police hunted for the friends, a woman noticed them gazing at the expensive sports cars and asked them what they were doing.
The boys had reportedly prepared their escape for several days, digging a hole under a fence using spades from the sandpit.
It was unclear how much money they had brought with them. They were not harmed and were returned safely to their parents, who did not file a formal complaint.
Local education authorities fired the supervisor in charge at the time of the incident and gave the acting head a warning.
“This is considered a very serious violation,” said the head of the pre-school department of Magnitogorsk, Olga Denisenko, told Komsomolskaya Pravda.
The Chelyabinsk regional interior ministry confirmed the escape, which happened several days ago, with a spokesman saying: “We don’t have any details yet, we can only confirm the fact itself”.
Once they had managed to dig their way to freedom, they set off on a kilometre-long trek to a showroom selling luxury cars.
When approached by a concerned woman near the showroom, the boys said they wanted to buy a vehicle – but lacked the funds.
Their absence was not noticed for another half an hour, when teachers raised the alarm.
The children were initially taken to the city’s Ordzhonikidze Police station.