I don't know. But it for sure isn't being the second best paid in the squad.
I don't know the numbers.
But Suarez played here for several years, he knew the team, teammates and tactics.
Aguero will be a new guy here, coming from a season long injury with a very questionable fitness.
Further, Suarez was able to play 40-45 matches per season for 90 minutes.
Aguero is rumoured to be a super sub.
Now, if Suarez had wages, let's say 15m (I don't know the numbers), then imo, Aguero would be a good deal only at 5m wages, based on his fitness and injuries.
If Aguero will get 10m compared to 15m from Suarez, that is a lower wage, but it is still a bad deal since we are probably getting way worse/injured/finished player than Suarez.