Depends on A) how bad you want it, and B) what the market is like in your area.
Around here, a good pre-safety 336 can still be found for under $300 with a bit of patient searching -- sometimes well under. A good friend bought a 1971 336 just a few weeks ago ("closet-abused" and showing lots of dust, a few dings, and some areas of very light rust, but mechanically as-new) for $150. A good Single Six will bring twice that, at least.