How much do these retail for nowadays?
0.03BTC
bitmain stopped selling them a few months ago. I sold one around a month ago for ~$120 shipped within the U.S. It's value has declined somewhat due to the increased difficulty that we saw last time around.
If you do win the auction then you will need a PSU to power the machine which tend to last a long time and can most likely be used long after it is no longer financially viable to continue mining. There are no details in the OP but a S3+ should hash at between 450 and 480 GHs at stock speeds and consume ~350ish watts at stock (I think this is right).
Unless you have very cheap or free electricity then it will probably not make sense to continue to run a S3+ for very much longer (probably not more then a few months depending on a number of factors).