Keep shopping - sometimes there are some great deals on ebay every so often! I've seen a few Zeiss PQS planars go for under $400 but a lot go for closer to $1000 some even over that. There's a big range. The funniest thing to me is that sometimes the zeiss 80mm versions fetch higher prices even though they are inferior to the Schneider's IMHO because of the typical zeiss chromatic doublet bokeh and higher distortion. That's why I have planar priced in the 6's. If were selling the Schneider, I'd ask for more.
If you are concerned about price the PQ planar versions are very similar optically and its got to be the cheapest 80mm for Rollei out there except for the few Rolligons that come up. I've had six total 80mm lenses - 4 Schneider (80 PQS, AF 80PQS, 2x 80/2) and only two planar's a PQ and PQS and all have been very sharp, but you have to watch out for fungus and other issues. Look for paint wear marks on the lens faces to see if the lens has been opened for service.