Unlike the man who finds a hidden treasure in the previous parable, the merchant in the Pearl of Great Price is searching for treasure, fine pearls. The kingdom is like the merchant in this case, not the valuable pearl, but the “is like” refers to the whole saying.
The word ἔμπορος, merchant, refers to “one who travels by ship for business reasons” (literally, someone who boards a boat; BDAG), a wholesale dealer who travels and finds sources for goods to resell. This is not necessarily a shop-owner, more like someone who owns an import/export business.
The point is the man is on the lookout for valuable things he can purchase and make some profit from. By analogy, occasionally I will find a book in a used bookshop that I know is more valuable than the asking price. I might buy the book knowing that I can “flip it” in Amazon or eBay for some profit (which I usually use to buy more books).
How Valuable Were Pearls in the Ancient World?
Pearls were highly valued in the ancient world, in some cases more valuable than gold; Noland suggests we could change the image to diamonds (Nolland, Matthew, 566). But it is unlikely the merchant would sell everything in order to obtain an extremely fine one. This is another example of hyperbole in this parable. Pearls (μαργαρίτης) are listed along with precious stones (Rev 17:4, 18:12, 16) and with gold (1 Tim 2:9).
Pliny the Elder said pearls have the “first place” among valuable items, the “topmost rank among things of price” (Natural History 9.106). “Among the Indians worth 3 times as much as pure gold: Arrian, Ind. 8, 13 and always in great demand: ibid. 8, 9)” (BDAG). Pearls from India were introduced into the Mediterranean area at the time of Alexander the Great and are not mentioned in the literature of Egypt or the Old Testament prior to that time.
Sell Everything to Gain the Kingdom
When the merchant finds the ultimate valuable pearl, he sells everything to purchase it. Since he is a businessman, this means something like “he liquidates his assets.”
Like the Hidden Treasure, the parable of the Pearl of Great Price is also about the cost of discipleship. Here is no need to allegorize this pearl to make it the church (Walvoord, Matthew: Thy Kingdom Come, 105) or Christ (Pentecost, The Parables of Jesus, 60). If anyone wants to follow Jesus, no price is too great to pay. ““the glorious character of the kingdom brought by Jesus, which justifies the cost of absolute discipleship (Hagner, Matthew 1-13, 396).”
There are some disciples of Jesus who were genuinely searching for the kingdom and found it in Jesus. Perhaps these are the disciples of John the Baptist or some Pharisees who responded to Jesus (Nicodemus, for example).
The Hidden Treasure described the disciples who unexpectedly find the Kingdom of God in Jesus’s ministry, The Pearl of great price described a disciple who was diligently searching for the Kingdom and also finds it in Jesus’s ministry. In both cases, the finder has something far more valuable than they could possibly imagine.