Given the current market situation I think the prices are not that bad, though I would need to be sure they are in good condition, and recently CLA'd. If they've not been serviced for quite some time, then a discount of $250 or so would be reasonable. All other things being equal, I'd buy the Xenotar if I were you, not because I know its better, but because you may get it cheaper, and I've seen no evidence its any lesser a lens than the Planar. But ultimately the one in the best condition wins, always.