Sorry brothers, I've been away for few days. For a 250CC bike i think you need to have 150K (good condition). The condition of the bike (engine+body) pretty much decides the price. If you go for an illegal one this will come close to 70 or 80 again i'm talking about good condition because believe me you don't want to glue yourself to mechanic after purchasing the bike.
The bike in my avtar is my previous bike which i have sold and it was a Honda CBR600rr now i have a Honda CBR954RR which worth lot of money. (really don't want to share the price cuz i don't people to mis-comment on it)