I made a scattergraph (Car price Y; Km X). It is ok for comparison at say a given level of Km, but as prices are scaled from $4000 to $7500 and 0 to 120 kliometers it is a little artificial in so far as an extra $1000 might get a car that has done 40,000 fewer km .

I'm wondering what statistical/ mathematical measures I might use to squeeze more out of the data.

Hope that's not confusing, thanks
John