RAM isn't cheap (it may be for your tasks and wallet depth, but generally it isn't, especially since DDR5). Shared objects also get "deduplicated" in RAM, not just on disk.
What objects is the Zed process using that would even be shared with any other process on my system? Language support is mostly via external language servers. It uses its own graphics framework, so the UI code wouldn't be shared. A huge amount of the executable size is tree-sitter related.