Bad price.
I paid $600 for mine. It had been sitting for 2 years in the Florida sun with a full tank of gas in it, and didn't even turn over (dead battery). It was missing the two side covers as well, but was all there otherwise. The paint was/is shot (it's faded bad) and the fork seals had long sense rotted away. The tank was -extremely- rusty on the inside as well, but thankfully still solid.
I paid to much for it, probally by $100 to $150, since it cost upwards of $500 to get it running and rideable (full carb overhaul, new timing chain, new oil pan gasket, new exhaust gasket).
Currently I'm probally in the middle of sinking another $1000 into it, or more. A complete GSXR front end is going on, as are new tires, GSXR 400 cams, plus a full racing exhaust (if it ever shows up).
I will say this for the 400, though. If the engine was maintaned even remotely well, it's nearly bulletproof. Both my mechanic and myself were pleasently surprised to find my 13800 mile motor was spotless on the inside with dead-on compression, even though the bike had been abused by an ignorant prior owner.
I got lucky, the Digital Igniter box on mine was fine. The majority of the 'dead' Bandit 400's you'll find will have dead Igniters. These are -not- a part you can get cheaply, your looking at something like $300-400 to ship it out for an overhaul. I believe there are two companies that do it, one in England and one in the Netherlands. If the bike has spark, chances are the igniter is fine, but even then it's only 100% ok if the engine fires and runs. Some people have had luck rebuilding them on their own with the directions posted on this site, but some people have not.
That said, the 400 Bandit is an awesome bike. I'd take it over a GS500, Ninja 250/500, or SV650 anyday!