Hoops boss Neil Lennon revealed last night the club had rejected a second bid from Norwich.
Lennon also confirmed Hooper – who has 18 months left on his deal – had turned down a new contract offer but the manager was confident he would still be a Celtic player on February 1.
However, Caldwell – who quit Parkhead for Wigan in January 2010 – believes any club that does succeed with a bid will secure themselves a bargain.
He said: "Having seen the players down in England, I think he would do really well, he would score a lot of goals.
"The clubs who are looking at him now would definitely get a bargain."