$150/160 per set with 180/55 or 190/50 respectively. Front tire is 120/70-17 in both sets.
Somewhere around Rosso/Angel GT territory. Not the most expensive tires anyway, but this is still ~$40 less than street price for the set. Could be older tires, probably nothing like some of the old tires you find on Ebay though. My guess is they'd be up to 2-3 years old which is fine. I have no knowledge of this. If you order a pair and are concerned be sure to check the DOT date molded into the tire.
http://www.bikebandit.com/tires-tubes/motorcycle-tires/pirelli-diablo-supersport-motorcycle-tire-set?u1=59481be0b68d11e5b8d6365477bc8f670000&id=lw9MynSeamY