Daniel Levy has defended Tottenham's transfer policy and insists the club will not sign a player this summer unless they are convinced he can make a difference to the squad.
Spurs are yet to make an addition despite selling Kyle Walker to Manchester City for over £50m, but Levy insists manager Mauricio Pochettino would rather use academy players than bring in new faces for the sake of it.
Speaking in New York, as he opened the Nasdaq stock exchange ahead of Tottenham's next friendly against Roma, the Spurs chairman also says the cost of their new stadium is not influencing transfer policy.
He said: "Regardless of the stadium project, today our position on transfers is that we have a coach that very much believes in the academy.
"Unless we can find a player who would make a difference he would rather give one of our academy players a chance, so that's regardless of the financing of the stadium.
"At the same time, the academy is important because we can produce our own players. We don't have to go and spend £20m, £30m, £40m on a player, and obviously that homegrown player has an affinity with the club that a player we buy doesn't.
"That's what the fans want to see. They want to have that passion. That's what you get with a homegrown player and that's why people love Harry Kane and sing that he's one of our own.
"Obviously when you're building a stadium of this magnitude in a UK context it all has to be privately financed. There's no state help whatsoever.
"It is a challenge and we have to find the right balance, but it's not impacting us at the moment on transfer activity because we're not yet in a place where we've found the player who we definitely want to buy but can't afford to buy."
While Spurs remain calm and patient, their top-four rivals are committing vast sums on big signings, with Manchester City, Manchester United and Chelsea all having taken their totals to over £100m with a month left of the window to spare.
But Levy said: "My view is that it's totally unsustainable. I'm not sure if that's the view of the other Premier League clubs, but certainly the prices that are being paid for other Premier League players I can't see being sustainable in the long term.
"I think I am a custodian of this football club. This club has been around since 1882 and, when I leave, it will be somebody else. I think we have a duty to manage the club appropriately. I don't think that long-term, for any club, it's sustainable to spend more than you earn. You can have periods where you do but over the long-term you can't.
"I think that some of the activity that's going on at the moment is just impossible to be sustainable. You know if somebody is spending £200m more than they're earning then eventually it catches up with you. You can't keep doing it.
"We've managed the club, we think, in a very appropriate way. We've invested a lot of money in physical facilities for long-term growth. So we've got one of the world's best training facilities. We've invested over £100m in that facility.
"We're now investing in the stadium. The stadium is fundamental because with that we get more fans and more income and that's the way to clearly have a more sustainable business."