Chicken and egg, though - as someone who has never owned a car, i wouldn't know which model to look at!
Is there scope for a levels.fyi for cars?
yes, and IIUC it's already a crowded market. I haven't been car shopping in a very long time so I'm not sure what's the current state of the art, but the Kelley Blue Book (edit: mentioned in a sibling comment) is probably the original and best-known one. First published in 1926, online since 1995.