If you don't anticipate the bike being stolen on a periodic basis, the correct dollar value of a "suitable commuting biker" depends strictly on the finances of the commuter.

Personally, I'm never going to ride a junker all week to "save" my nice bike for my non-existent weekend rides.

He's a fun fact: The bike that I ride to work is worth at least three times as much as the bike I race with.

Strange, but true.