Some hypotheticals to make this fun:
Spurs finish 3rd in the league. Over the summer they sell Modric to Manchester United for £50 and Bale to Real Madrid for £80 million (I figured that was more realistic than the £150 million price tag Spurs have placed on him).
You're Dan Levy. You've just lost your two best players, but are now sitting on £130 million to reinvest. Taking into account Tottenham Hotspur's wage limits (let's say £100,000/week salary cap), can you wheel-and-deal that £130 million to improve the team over their current level?
The basic question here is this: are Spurs a better team with Modric and Bale, or with the £130 million reinvestment their potential sales would provide? And if the answer is "with Modric and Bale", what amount of compensation do you think it would take to make Spurs a better squad in their absence?