The Ivorian international is out of contract at Stamford Bridge in the summer and has been linked with a move to the lucrative Chinese league.
Redknapp admits that this could be a stumbling block to any deal as Spurs and other clubs may struggle to match the wages offered by clubs in the Far East.
"He is a free but I was just reading in the paper about him going to China. It seems the money in China at the moment is incredible. Players can go there and make a fortune," said Redknapp.
"He would be a great player for Chelsea to keep or for somebody else to take. Anyone would be interested but you would have to be able to afford his wages.
"That is going to be the key. If he is on a free you are going to have to pay him a fortune."
Drogba scored against Spurs in Chelsea's 5-1 FA Cup semi-final victory last weekend.