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."
Vertonghen joined Ajax in 2003 and progressed through their youth academy to become skipper and played a leading role in the club retaining their Eredivisie crown this season.
And while he admits it will be a wrench to leave he is hoping his loyalty will be repaid.
He added: "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."
Vertonghen believes he would fit in nicely at Tottenham.
"Tottenham is a fantastic football club. Ajax was the perfect club for me, but Spurs will be very close in nearing that already. They buy young, eager and offensive-minded players."