Again, the kingdom of heaven is like a merchant in search of fine pearls, who, on finding one pearl of great value, went and sold all that he had and bought it. (Matt 13:45-46, ESV)
This parable really is paired with the last, and the two have a similar theme: once the kingdom of heaven is discovered, you must be willing to sacrifice everything to gain it.
The only real difference between this parable and the one before is the nature of the discovery: in the hidden treasure parable, the discovery was made by accident; in the pearl of great price, the discovery is made after diligent searching. The larger point being, of course, that regardless of how you come to be introduced to the Gospel of Christ, there is a sacrificing of everything that you have and are in order to gain the treasure of immense value.
Also of some note here is to understand that at the time of Jesus a pearl was considered of much more value than it is today—pearls were truly extravagant. They play a role in nearly every ancient religion: Muslims picture those in Paradise wearing pearls; Hindu kings wear pearls; in Matthew 7:6 Jesus compares the gospel to pearls; in Revelation 21 heaven’s gates are described as pearly.