Carson, who has joined the Baggies from Anfield after spending last season on loan at Villa Park, believes the time is right for Barry to move on.
"I think if he wants to leave he should really," Carson told BBC WM.
"However, people have got their price and if Liverpool cannot match the price then they have got to come to some sort of agreement."
Carson had been linked with a permanent move from Anfield to Villa this summer after spending last season on loan with Martin O'Neill's club.
The Villa manager now appears to be opting for Blackburn veteran Brad Friedel.
"They never said that they definitely didn't want me, they said they were going to go for an experienced one and maybe they still will," said Carson, who cost the Baggies £3.25m earlier this month.
"Obviously, I couldn't go somewhere to be second choice - I would have been better off staying at Liverpool - but I think the time was right to leave and get settled."