I would think its not good for Spurs, Spurs are doing well buying the likes of Carrick/Berbatov/Modric, then selling them on for a profit. Spurs will have a much harder time being long term competitive if they start spending silly money on big players who expect huge wages to go along with a huge deal. They don't have the income from the stadium/corporate/commercial that the clubs above them can come up with.
Spurs would do much better to buy someone vastly cheaper, get another striker, get another CB, get another fullback, etc, etc, than blow your whole load on one midfielder. Getting rid of quite a few people as well as potentially a couple more on loan before the end of the day. I might be forgetting some squad members but you've got next to no back up at wing, fullback, constantly problems at CB due to injuries, upfront... even more so if Defoe is sold which is looking less likely at this point.
DO'h, keep forgetting you got Dembele, not entirely sure where he'll play for you, his versatility will certainly help you out. Though again with his best performances of late coming in central mid, filling up central midfield might push Dembele somewhere else, wing maybe, 2 upfront? Play as a withdrawn striker leaving Sig for the bench?