My first prototypes are around that cost (not including assembly, granted) and have a richer feature set, as well as a smaller form factor that doesn’t require the annoying rubber ducky antenna.
The module you linked to doesn’t come with software of any kind, so chances are you still need an expensive compiler toolchain (Texas Instruments requires IAR) and potentially a programmer / debugger. There is an open-source compiler for 8051 based MCUs (like the CC2430) called SDCC, but I am not sure if it’s mature enough to compile Z-Stack, which is TI’s own ZigBee library. Up until recently it wasn’t able to produce good enough binaries, but SDCC is under active development, so chances are the situation is better now.
Also, the module you linked to doesn’t come with FCC certification or MAC address allocation, so I am left with the same problems as with my own prototype.
The head-start I would get from using a module such as the one you linked to is marginal.
The only off-the-shelve module that comes close to my requirement is Pinoccio. It just needs different firmware, but it also comes with a whole bunch of unnecessary (for this application) features, which significantly drive up the price.