It is immediately obvious that the Parable of the Pearl of Great Price and the Parable of the Hidden Treasure are similar; they have a similar form and similar symbols. They both tell the same basic story. It is interesting that in this series of parables, Christ gave two that are so much alike. This is not unusual.
In Genesis 41:1-7 are Pharaoh's dreams about the upcoming famine. Notice that God gave Pharaoh two similar dreams: a vision of seven healthy cows devoured by seven gaunt ones and then seven good heads of grain devoured by seven blighted ones. He did this to emphasize matters to Pharaoh. Repetition is the best form of emphasis.
In addition, He did it because something appeared in the second one that was not in the first, and it was an important factor for Pharaoh to understand. What it told Joseph is that there would be, not only a famine that affected livestock, but also a famine affecting vegetation. It would be a total famine, and they had to prepare accordingly.
In these two parables, then—the Hidden Treasure and the Pearl of Great Price—there must be something additional in the Parable of the Pearl of Great Price that is not quite understandable from the Parable of the Hidden Treasure. Jesus gave a second parable with a slightly different meaning for a reason: to give us encouragement.
Richard T. Ritenbaugh
Parables of Matthew 13 (Part 3): Hidden Treasure