Sadly a PSN just like that sold on ebay for low $200's while a much lesser Ventoux sold for upper $200's. There's no rhyme or reason for why that happened. The PSN was poorly advertised with crappy picture so that may have had something to do with it.
I wouldnt let the PSN go for a dime less than $200. Heck, parted out the frameset could bring $200.
Your P18 looks to be in excellent condition. Again, prices are all over the map...$50-150