In my 2019 MP I have 40TB in the J2i bracket, 2x Sonnet PCIe cards with 8TB in each (4x 2TB Samsung blades), and one Kyro PCIe card with 2TB Samsung SSD blade, and wheels. These collectively came to around $5,500. All of these accessories will transfer to the 2023 MP, along with their data that means no huge amount of time required to transfer close to 50 TB. The 2019 MP wheels can be transferred as well.
For me the upgrade to the 2023 MP makes more sense that upgrading to a M1 Ultra Studio.
In addition the 2023 MP's internal SSD can be upgraded without much ado.