The Magpies sold Toney to Posh in 2018 for around £300,000 after series of loan deals around the EFL but he stormed to success at London Road, grabbing 49 goals before winning a big money move to Brentford this summer.
Toney played just a handful of games on Tyneside before his sale was sanctioned during the Rafa Benitez era.
Peterborough United co-owner Darragh MacAnthony, speaking to Hard Truth podcast, said: “Ultimately we have pulled off close to a miracle in getting such a fee for a player in the middle of a pandemic.
“Newcastle do have a massive sell on which is fine."
He added: "I'm happy to help Steve Bruce's transfer budget this summer.
"Newcastle were great to deal with two years ago when we signed Ivan and they were great to deal with again in the last few weeks.
"We actually still owed them £100k on the original deal as we were paying in instalments!"