The Belgium international is likely to have played his last game for Ajax in Sunday's 3-1 win at Vitesse Arnhem and has been linked with a move to White Hart Lane.
Vertonghen has just one year left on his current deal and appears keen on a switch to the north London club.
The 25-year-old told De Telegraaf newspaper: "The board is asking a fair amount for a player who is only contracted for another year. I trust that Ajax and Spurs can turn water into wine and sort it out soon.
"I owe a lot to Ajax but I have always given my heart and soul. My appreciation for the club and fans is great and it would be terrible if my farewell was marred by Ajax sticking to a great price.
"Of course I want Ajax to gain financially but the amount Tottenham are willing to pay - perhaps with a little extra - is very reasonable."