To dream of a sale or that a certain object is on sale represents opportunities or experiences that are easier than they were previously. A barrier or obstacle has been reduced. A situation where less is being asked of you to achieve the same goal or objective.
To dream that you put something on sale may reflect lowered expectations or just wanting to get something done quickly.
Negatively, putting something on sale may reflect how you are not believing in yourself enough or are underestimating yourself. It may also reflect feelings of desperation.