The former Borussia Dortmund striker moved to City for £51m this month.
Haaland joins on £375,000 in weekly wages, but Soriano insists the Norwegian made a football decision by joining the Cityzens.
He said: "The fee was agreed by the release clause and a lot of clubs were willing to pay his salary demands.
“I'd say the key point was the technical discussion about football — and how he is going to fit into this machine that works.
“We've won four leagues out of five, we've scored so many goals, he had to feel that he could get into it."