Bale won't go, the closest to leaving he'll get is if Levy agrees he can go in a year.
AVB is a class manager, he's made statements this summer when linked to PSG/Barca that he's fully committed to spurs and this will be partly because he's been guaranteed Bale is staying no matter what the offer is. He's said a few times Levy has guaranteed Bale won't go. If Levy went back on this and sold AVBs best player the relationship would break down and he'd end up losing AVB next summer, not hat Levy wants, he's a big fan of AVB.
Similar for Paulinho, he stated he was told Bale would not be sold during his negatiations with Spurs.
Further, spurs are actively trying to strengthen their team. This is difficult since they don't have champions league. Having Bale and keeping bale is a big sell, it means they're really going for it this year.
In terms of income Spurs don't need it, if they sell bale for 100m they'll be cash rich but they'll struggle to bring any stars in and will effectively cement 5th place before the season starts so they'll miss out on champions league money. Given the spend from City, Chelsea and the new threat that Arsenal might spend this is a big year for spurs, if they get left behind they could be looking at years outside the top 4. After having years of it already that's probably what's prompted Levy to spend big this year to finally bring 4th place home and try and cement it long term.
Alternatively spurs keep bale, make some signings, aim for a big season, if it doesn;t work out they can sell bale next summer and in a world where Monaco, PSG, barca, madrid, chelsea, city, the russians and now even napoli and arsenal throwing huge bids around Bale's an easy 50m so there's no big risk in his value of not selling him, ignoring the constant risk of career ending injuries etc.
keep bale, try to break into the top 4 for good, that's what they're doing. Plus Bale's not gone public like suarez and he's a settled family man, no pressure to sell.