Re: Type tc cable for panel feeder
Section 336.2 of the 2002 NEC appears to indicate Type TC cable is only to be "installed in cable trays, in raceways, or where supported by a messenger wire."
I'm not exactly sure if tray cable has the same fire-propagation and smoke-release characteristics of NM and SE cable.
Cost should not be your primary concern. I would consult your local AHJ.