[Non-Sequitur]

I think that later on, owners would have been more conducive to the idea. And the cost would be much less than what it would cost to fight the most destructive war in US History.

In retrospect, yes. But without that alternative to compare it to then any cost would have resulted in sticker shock. And it would still be a case of the government up North telling southern slaveowners that they had to give up their chattel becuase the government said so. The idea of that happening was important enough to rebel over in 1861, how much longer would it have taken before the south didn't believe that their 'peculiar institution' was worth fighting for?

[TexConfederate1861]

Most experts agree that slavery would have gone the way of the Dodo by 1880 or so. It wouldn't have remained economically feasible after the industrial revolution.