Adding USB thumb-drive support to existing product

I'm evaluating adding USB thumb-drive support
to an existing product. The product has a RS-485
LAN; I'll add a new LAN node that interfaces to
the thumb drive. BOM must be under $30; as always
lower would be better.

To do this requires:
- host USB support
- USB basic software stack
- USB thumb-drive (FAT etc) software stack
- serial port (9-bit capable for our LAN)

I'm considering using a uC we already use plus
the FTDI Vinculum part. Quick development, probably
can meet the BOM (VDRIVE is ~ $25 before qty
discounts, our own board with FTDI controller
would be cheaper).

Anybody got an alternate uC they'd suggest, which
includes all of the above, is available in eval/
devel boards including USB host, has conventional
and robust C development tools, and does not require
$$$ for the software stack and/or tools ? And has
all the required libraries to do file IO to the
thumb drive ?

Thanks in advance for your inputs !

PS: Requirement Notes:
- USB thumb-drive (NOT compact-flash or other storage)
- microcontrollers with proprietary languages
(instead of ANSI C as our existing code requires)
are disqualified (to minimize port work)
.