puntz,

My own opinion is that it is not the actual price but the structure of the betting on that particular race.

e.g 5 horse race biggest priced horse 6/1 then he is the longshot.

e.g 16 horse very open race, 1st 6 favs 6/1 to 8/1 then I would suggest the long shot is outside of these.

Just my thoughts

Cheers