People have a warped expectations on figures, just because PSG spent £200m on Neymar and £160m on Mbappe doesn't mean that's the norm. For all other clubs outside of City, clubs have to spend using their actual own revenue and can't throw out lavish sums using oil wealth.
Coutinho and Dembele only went for high figures due to the Neymar money Barca recieved.
If you exclude the Neymar saga, the top-end transfers for a top player like Frankie De Jong costs £70-80m. Sancho's young and has high potential, so you can say he'll go at a premium, which will put him at around £100m (higher than a Pogba 2 and a half years ago).
People expecting £150m bids are crazy, very few clubs have spent that in a single summer on multiple players ever, to expect it to go on one player is ludicrous. True Dortmund don't have to sell, but there isn't a cue of clubs waiting to bid £100m+ either. Madrid have been reluctant to spend big on Hazard who's ahead of Sancho because they want to wait and get him at sub £100m. Barca, City, PSG and Liverpool don't need him. Who does that leave? Chelsea if they sell Hazard? Madrid if they don't go for Hazard? The most realistic situation is that a club bids £80m - £100m, and one of two things will happen 1) Sancho will force a move for the far higher salary he'll get in the PL vs what he'd get for Dortmund, or 2) Dortmund reject it and Sancho's content to continue progressing in the Bunedsliga.