Blockade boat owners turned to engines for speed instead of sails. Blockade running became more expensive as the blockade became stricter. Certain prices increased much faster and higher. Most goods desired in the South had to be imported.
Luxuries were available, but necessities were not, because the fixed costs of transportation made it more profitable to ship high end goods rather than low end. Essentially, luxury items became cheaper to import relative to necessities. This was the Rhett Butler Effect which was really the blockade effect.
Lecture 4 of 8 from Mark Thornton's The Economics of the Civil War, presented to the Auburn University Academy for Lifelong Learners.