If you watch & listen closely to the scene...money wasn't really what Sollozzo wanted from the Corleone Family. He was being backed financially by Tattaglia and of course, Barzini. What he clearly states during that meeting is that he needs Vito's protection from the judges and politicians that he holds in his pocket 'like so many nickels and dimes'. That is what he was denied when Vito turned him down.

When Santino spoke out of turn, Sollozzo sensed that a new, younger Don would be more cooperative. That is why he needed to have Vito dead. As a purely business move, so that he could then deal with Don Santino Corleone...which is why when he had Vito shot and presumed dead, he convinced the kidnapped Tom to reason with Sonny into making the deal on the drug business.

Apple