Auba is a must even at £65m. There is a level of forward players in that elite bracket behind Messi & Ronaldo and they are Suarez, Neymar & Aguero + arguably Lewandowski. Lewandowski wouldn't fit in the same team as Aguero and the other 2 are unobtainable. This guy is in my opinion almost at if not already at the same level as those others and he is flexible enough to play anywhere in the front 3 as well as being more than good enough to play centrally when Aguero gets injured / rested.
When a player this good is available you have to take them. Trying to negotiate with Dortmund is fair enough but not at the risk of missing out on this guy. KDB is the only player in years that we've signed who has vastly improved our first 11 and we had to pay top dollar for him. Real paid more than this for Bale and around this figure for Rodriguez. appreciate that we have to strengthen in other areas too but we have to make an exception and pay more than we usually would for a player of this quality.