Thinking with bioremediation is a good choice if you  have enough time to wait. Myself I prefer the collection of of the oil with the aid of floating belt and moving it to the sea coast or river sides. This ensures both economy and environmental protection. I agree with Augustine that we need to consider all the variables.    

I concur with the first two responses in that the correct 'answer' will depend on the type, extent, location, etc of the spill.  Bioremediation is the most cost effective approach if time is not critical.  Collection of the oil on surface water can be done with belts.  On soils a surfactant would be necessary to enhance recovery.

Kindly note, that large scale oil spills from the oil and gas industry next to metals such as mercury, commonly contain heavy oils with large C-number, also asphaltenes and waxes which is not suitable for bioremediation. Cheap alternatives is a dream, only.