SODIMMs use a 64 bit wide memory bus. The TI AM62x SOCs only have a 16 bit wide memory bus. There exist modular memory which can work with narrow buses like this but it's not common or inexpensive. Most embedded SOC are meant to be used with a "memory down" configuration where the memory is soldered to the same PCB as the SOC.
Additionally, there's only 2GB of the DDR which is accessible to all of the processors within the SOC. The Cortex-A processors can use the addresses beyond 32 bits but because only 2GB of the DDR is within the first 32 bits worth of memory mapping, the other processors cannot easily access memory beyond 2GB.
$100 is an amazing deal when considering this as a development board or reference design to build a real product from. $100 is not that great a deal if you want a Raspberry Pi replacement. Different markets and different use-cases.
Additionally, there's only 2GB of the DDR which is accessible to all of the processors within the SOC. The Cortex-A processors can use the addresses beyond 32 bits but because only 2GB of the DDR is within the first 32 bits worth of memory mapping, the other processors cannot easily access memory beyond 2GB.
$100 is an amazing deal when considering this as a development board or reference design to build a real product from. $100 is not that great a deal if you want a Raspberry Pi replacement. Different markets and different use-cases.