PINE64 has started selling the SOQuartz Compute Module W, a device that could be used on its own or as a carrier board for the Raspberry Pi Compute Module 4. The system on module starts at US$34.99 and is orderable now with up to 8 GB of RAM.
https://www.notebookcheck.net/PINE64-SOQuartz-Compute-Module-W-US-34-99-system-on-module-launched-that-can-be-used-as-a-Raspberry-Pi-Compute-Module-4-carrier-board.577956.0.html