An extreme few, if any, plantations survived the civil war and remained in farming as large plantations. But to compare 'profit' of the plantations before and after the war, is nearly impossible, as it tries to compare such extremely different circumstances. The main difference being, that before the war, profit was made, while after the war, farming was done largely for survival.

While the end of slavery meant plantations would have to work differently, remember that only 1% of citizens in the US owned any slaves at all, and they were naturally the richest 1%. A much bigger impact than freeing enslaved workers, was put upon southern plantations toward the end of the war, by the destruction caused by the war.

The years of war of course had taken a toll on the south more so than the north, for many reasons. But as it dragged on, in order for the North to bring an end to the war, the North had to nearly destroy the southern states in order to bring about the surrender of the undaunted Confederate Army. Between the North's slash and burn treatment of towns and farms and railroads and industry, and Sherman's March to the Sea creating a wide swath of destruction, and the years of economic distress caused by the war, the southern states experienced an economic destruction that they in fact, have not yet recovered fully from to this day. Such was the extent of the destruction. Industry was destroyed, farms destroyed, and even the means necessary to move product, such as roads and bridges and railroads were destroyed. The South was devastated physically and economically.

Plantations that survived being destroyed, did not go back into large scale farming. Firstly, the immediate need was for subsistence so they didn't starve. As starvation became less of a danger, running of the farms fell largely to women left behind, or returning male survivors, who negotiated with former slaves to keep bare minimums in operation. As food stuffs began to be produced again, and then later crops that could be sold, the farm owners rented the freed slaves land or paid them wages, along with any white families who had been displaced from destroyed towns or areas that were worse off, or other reasons they were looking to relocate. And large portions of plantation lands, and whole remaining plantations, were often sold off to carpetbaggers (profiteers) who came down from northern states to profit off the south's unfortunate circumstances.

The period known as the Southern Reconstruction was an extremely difficult time as the south struggled to get on its feet again. Historically, the southern reconstruction era is earmarked as ending around 1877 when the Federal troops occupying the southern states, finally were withdrawn, BUT the south was still a long way from being rebuilt.

Take a look at these images.

http://tinyurl.com/pjwbpqc

Those are the ruins of Richmond after the war. THAT is the scale of destruction which the southern states had to deal with. And they -still- haven't recovered fully, especially economically. To this day, the southern states, and the people living in the south, are poorer by far, with far fewer resources, than the northern states which forcibly put them so far behind.

To compare a facet of southern pre-war living in any way to the post-war environment in the south, is just not possible. Even though its the same geographic area, the two time periods are in two drastically different worlds.