The Brazil international was a transfer target for Ernesto Valverde last summer transfer window. The Catalan club's multiple approaches were turned down despite the player handing in a transfer request at Anfield.
Barcelona were successful in landing their top target in the mid-season transfer window. Coutinho completed a move to Camp Nou and signed a five-and-a-half year deal with the La Liga leaders.
"Philippe Coutinho is not worth that [£142m], he's not that good," Carragher told Sky Sports' The Debate Show, as quoted by The Sun.
Barcelona and Real Madrid have raided the Premier League in the past to take the best players from the league in England. Cristiano Ronaldo left Manchester United and moved to the Spanish capital club in 2009 while the Reds saw Luis Suarez join Real's rivals in 2014.
Both the deals took place in the summer and not during the course of the season. However, Liverpool sanctioned Coutinho's sale in January, while adding Virgil van Dijk to their squad. The Dutchman became the world's most expensive defender as he arrived at Anfield from Southampton for £75m.
Carragher was unhappy with his former club's decision to sanction the ex-Inter Milan man's sale in January, especially when they were in contention to challenge for the Champions League and the FA Cup. Liverpool were knocked out of the cup competition following their 3-2 defeat to West Bromwich Albion late in January.
"I think if you lose your best player there's no way you can dress it up as a positive window, certainly in January as well," the former Reds defender explained.
"I think every Liverpool fan, myself included, when Philippe Coutinho stayed in the summer, felt okay. We know he's going next season, let's enjoy these 12 months, probably similar to Ronaldo, Luis Suarez, you always felt that was going to happen.
"To lose him mid-season, you know I don't agree. I would have took him at £20m, £30m less in the summer to know that Liverpool would have had him in the second half of the season, because at that time we're still in the FA Cup, we're still in the Champions League."