Final answer:
The increase in the price of slaves was due to the heightened demand for slave labor caused by the expansion of cash crop agriculture, particularly sugar and cotton, resulting in a substantial domestic slave trade and rising slave prices in the 1850s.
Step-by-step explanation:
The increase in the price of slaves was primarily due to the increase in demand for slave labor, which was fueled by the growth of cash crops such as sugar and cotton. Sugar, in particular, drove the world slave trade, especially in the Americas where plantations in Brazil and the Caribbean relied heavily on enslaved Africans for the labor-intensive production of this lucrative crop. Additionally, the invention of the cotton gin in the 1790s significantly boosted the U.S. slave market as cotton became a dominant crop.
Moreover, after the abolition of the foreign slave trade in 1807, a thriving domestic slave trade emerged, leading to an all-time high in the demand and prices for enslaved individuals by the 1850s, where prices doubled compared to the 1820s.