There are so many variables to consider. But you have to remember that it's only worth what someone wants to pay for it. If it's mechanically sound and has no major issues then maybe. You'd probably want to swap out the tires/tubes/cassette/chain and maybe even the cables, service the wheels/hubs and drive train (clean, grease and repack hubs, true wheels, adjust derailleur, etc). After that's all said and done you'd have a nice commuter bike and you'd have spent less than a big box bicycle that wouldn't last more than a few years of serious riding.

See if you can snag it for $50, and allow yourself $50-$150 for parts/tools (if you don't already have them).