My guess is that it is this 1983 PH10S. The link below shows the PH10S. Notice the slots in the crankset arms. The link shows the three bottom of the line bikes from that time with the P6 the bottom.

http://cyclespeugeot.com/images/1983...6_P8_PH10S.jpg

The price depends on the market, but does not seem unreasonable if it is in good rideable condition.