Rashford has long made it clear that he wants to remain at Barcelona beyond his season-long loan from United where he has a £26M release clause that could be triggered at the end of the campaign.
Barca have until June 15 to activate the option to make the loan permanent, but reports have suggested they will return to the negotiation table as they try to bring down the price.
Despite their bartering, Ferdinand has claimed such a fee is an absolute bargain and is almost a robbery for the Spanish giants.
"If Barcelona get him for the reported £26m that we’re talking about and they get that version of Marcus Rashford, that is an absolute robbery, it’s a steal," Ferdinand said on his YouTube channel.
"I just say good luck to him, I want him to do well, because I’ve seen him grow as a young player at United and good luck to him in that sense."
The winger has netted 11 goals during his time in Spain and assisted a further 13 in his 39 appearances across all competitions.
He has become pivotal for manager Hansi Flick who is a big admirer of the England star who is loving life away from the Red Devils.
After winning the Spanish Super Cup earlier this year, he will now be eyeing a league title, something United haven’t won for over a decade.