From the rumours it honestly seems that Alexis actually wants to stay in the Premier League and London which means that the Gypos are likely his second choice behind the Chavs.
But yeah I agree with the sentiment of your post - we hold a lot more leverage here then some think. City and Pep are clearly desperate for him and keeping him risks other clubs gazumping them with a mega money contract offer. Hence why that Sterling + cash supposed offer is purely laughable.