Looking back, West Ham bagged a bargain.
West Ham United's Michail Antonio in action with Middlesbrough's Calum Chambers
Forest had paid just £1.5 million to sign him from Sheffield Wednesday, a deal for which they deserve enormous credit.
But looking back at Antonio's career since, it looks like £7 million was terrible value for the flying winger.
Antonio scored 19 goals for Forest in his short spell at the club, and was clearly a player capable of kicking on at the next level.
At West Ham he has gone from strength to strength, earning an England international call up and becoming the club's most dynamic attacking player.
Antonio is now attracting serious attention from the league's big guns, with The Sun reporting last month that leaders Chelsea were eyeing a big bid.
Forest owner Fawaz Al-Hasawi has come in for criticism for selling the club's stars, but Antonio was one he could not hold back.
The fact he got just £7 million for him in the current market does not look great, especially considering that he landed a £13 million windfall from Red Bull Leipzig for Oliver Burke a year later - who had so far made less of an impact that Antonio had for the club.
The Nottingham Post reported yesterday that the club's latest set of accounts still show the club to have big debts, every penny counts, and selling low on Antonio is a mistake they should not repeat with their current stars.
Under pressure Nottingham Forest Chairman Fawaz Al Hasawi (L)