well i was just thinking if the voice message is predefined we can directly use some winbond ic's or apex ic's which are very cheaply and commonly available ....
apex9600 with 16 minutes of message recording and 8 triggers costs about 250 indian rupees nearly 5.4 USD
and is available at most of the electronics shops in bangalore india (even readymade PCB's are available for it) .. i have used it and is very easy to control too ... you can also configure it to record the messages on the fly i.e. when the main circuit is working ... apex also comes with lower versions of the same IC costing as less as 1 USD but they are OTP's.

keep trying and best of luck ...
if you come up with another cheaper solution let me know too :-) ...
just for information i had used it in a circuit where the guests can leave voice messages when they visit my place in my absence .... any more suggestions in the same regard are welcome

nitin