Base price is usually the model with the minimum amount of content (features), without options, and before Transportation costs. Depending on the car, could be the manual transmission model, with roll up windows, am fm radio, etc.
Base car means a vehicle that has no trim options, like say a Cadillac Deville vs a Cadillac Deville CTS, the CTS is a trim option. HTH
Basement features (Base), more deluxe features above the basement (base). Base is from the Latin, "basis".