Depends, it can take longer to mask everything than to actually paint. But it depends on how many coats, how many times you have to re-mask, how many colors etc., etc.. Once masked, one or two coats of sealer, two (or more) coats of base color, then three coats of clear can easlily take 6 to 8 hours.
The materials are the biggest expense nowadays! I spent over $1000 just for the sealer, one gallon of red base coat and a gallon of clear, along with all their associated activators, hardeners, reducers, etc. Paint prices depend a lot on color, red being one of the most expensive.