Tottenham is in a tough spot and there is no right answer IMO, although everything depends on where they plan on finishing in the league. If they feel like a top 6 finish, possibly top 4, is achievable then I could see why they think holding onto Kane would be a wise choice.
That being said I don't think they finish top 6. City, Arsenal, Newcastle, Liverpool, United should all finish within the top 5, and after that there is still Villa, Chelsea and Brighton to contend with. Tottenham still hasn't addressed their woeful defense, and you can't rely on Kane to score as much as he did last year (god forbid he gets injured) so those around him really need to step up.
Personally I say sell, re invest, and re build, as I don't think they have what it takes to make top 4 and losing Kane on a free will be a nightmare. No where in that squad will you find the personnel to replace what he offers, and Levy is notoriously cheap so how are getting a 100m Forward on a shoestring budget?
I understand that in a direct comparison the answer is no, but from a sporting perspective remaining in the top 4 is imperative and I'm sure there is some value there that is quite subjective.
I don't know how they compete in the market at this point in time, given how much their competitors are willing to spend on fees and wages. CL would help in attracting talent but that doesn't seem like a reality in the next 2 or 3 years.