The Ventoux (PH501) was the top of the line non-aluminum bike for Peugeot in '87 and had a Reynolds 501 main triangle and Huret Rival white color components (still it was a mid-level bike.) Does this sound like your bike? Hard to tell about the value of a saddle just by the color without knowing the make and model, but I suspect that it will not pay for a tune up, tires and tubes, even if it were brand new. In the condition you indicate, needing overhaul, tires, tubes and such, I'd say the value is around $100-150 depending on the market.
Here is the catalog page for your bike from miamijim's Peugeot site:
