This.
Comparing us to City/Utd is silly considering we actually have to watch what we spend to an extent whereas those two can chuck whatever money they can without any consequences or impact on their bottom line.
If Aubemeyang is the player we desperately need then losing out on him either to a rival or with him not moving over three million is stupid (I still have nightmares about the Higuain deal) but as long as the negotiation team have time, I can understand them trying to extract the best price for the club.
tl;dr - stop comparing the way we do business to the likes of City/Utd and Chelsea (though I think they're slowly morphing into us now). You're comparing clubs essentially playing football manager versus a club in the real world.