I think, if you really use the PDA as a PDA, and not as a mobile computing toy/device with some form of data access, the cost of the PDA quickly becomes negligible in proportion to the use of the device for storing important data.
I too considered various WinCE devices as a PDA to load linux, but realised that the Z was the shortest route to something that did the job. I still use my Palm T3 for some PDA usage and games.