I'm working on v2 of the Hack Clock, this time hopefully using the RaspPi Zero and the much more streamlined Adafruit I2S amp breakout. If you re-use some existing USB hardware, SD cards and spare wire, that means the total build could be less than $32. Not to mention the build would have a lower footprint.
I'm also hopeful that I2S proves more stable than the PWM -> audio jack on the Model A.
Draft parts list is at https://www.adafruit.com/wishlists/413935