The Toffees are known to be in the market for the Republic of Ireland international, who was taken to the DW Stadium by Roberto Martinez - the new man in charge at Goodison Park.
Wigan will not stand in the 22-year-old's way if an enticing offer is tabled, but will hold out for the best possible price.
Whelan has now revealed the kind of money it will take to land McCarthy.
He accepts that Everton could return before Monday's 11pm deadline - especially if they offload Marouane Fellaini - but is confident the Latics can react to any late movement if they are forced to go in search of a replacement.
He said in The Sun: "If Everton lose Fellaini and (Leighton) Baines, they're going to get their £38m or whatever. They've already made one offer for McCarthy, which wasn't good enough. Roberto knows what he's valued at.
"You've got to be talking £14m or more. Are they a long way off? Probably £2m, but we're sticking because we've got to replace him.
"That sounds a lot of money but when you look around at the moment, all the extra money in the Premier League, it's just going mad.
"If we go and look for somebody, it's starting at £5m-£6m.
"We're sat there and if Everton sell their midfield lad, Fellaini, they're going to come for ours. We want to replace - but can we?"