Slaves were a great capital asset class but could not be active consumers for industrial goods or borrowers from financial institutions. Wage earning labor could and did have money to spend and interact with financial markets. How important was it to the Northern financial/industrial elites that slavery end to free up a large capital asset and create more consumers for the expanding northern business community. Was this as important as the idea that slavery should end because it was "evil"?
i think there is a better reason why slave versus free labor caused the civil war: free labor free soil free men: the calling card of the republican party and the name of a great little book by Foner. Indeed the problem there was often that slavery was "evil" but also often evil because of the harms to placed on free whites due to the nature of slave labor.
also this question is essentially a controversial one that's going to break down on what school of thought you believe in though i would note your underestimating the value of slave labor and the cotton it produced to northern manufacturers throughout history. so essentially the slave/free dichotomy was a major factor for the civil war but even focusing on the financier and capitalist classes the arguments are often different from the ones you are setting up
First, you're conflating a couple of different ideas + trends. Northern financial/industrial elites didn't necessarily see the slave population as a missed consumer opportunity - since the idea that slaves were people and not property varied from person to person. As fifa-2002 said - southern cotton powered many northern mills so in many ways it was a beneficial relationship.
The idea that slavery should end because it was "evil" represents the abolitionist POV and not necessarily the views of most people in the United States. The idea that slavery was a great moral "wrong" didn't truly gain currency until the Emancipation Proclamation - and even then people accused Lincoln and his government of taking advantage of the situation (which they were).
At the end of the day - the Civil War resulted from a confluence of factors including 80 years of political conflict, political compromise, structure, economic measures (tariffs), and political extremists actively pushing for a break with the United States. The idea that northern financial and industrial elites pushed the conflict isn't usually cited as a driving reason for the conflict - but certainly influenced some politicians reactions.