The economic viability of slavery and it's eventual abolition

I felt like doing some historical research and found some interesting information in regards to slavery and how economically beneficial it was financially to farmers up until the Civil War. I found an interesting correlation between prices of slaves, wages paid to farm labor in non slave states, and the abolition movement.

It seems that perhaps a large reason for the abolition movement was due to slavery no longer being financially feasible compared to just hiring labor. I find it interesting that once it wasn't cost efficient, all of a sudden it was this terrible thing that needed to be done away with. But all the years prior, people found a way to justify it.

Take for example, from the info I gathered, farm wages in the midwest in 1820 were around 9 bucks a month with board. 108 dollars per year. A prime slave was worth about 250 dollars at that time. Average lifespan on a plantation was 7-9 years for a slave. So basically after 2 years, you had free labor for 5-7 years. Cost efficient.

After 1850, costs of a slave skyrocketed to 1600-2000 dollars due to other countries cutting off the Atlantic trade routes. At the same time, farm labor was about 15 dollars a month. A slave would have to work for around 10 years before the cost justified themselves, and since many died earlier than that, it was no longer cost efficient. Right after this change in pricing, the push for abolition started.

Just find it interesting how money drives evil and leads to justification of said evil, and the moral high ground is only taken once money it no longer in the equation.