It worth spending the money on a great microphone as it is proven that you can get away with a low quality video or graphics but bad audio will kill your video or project.

I prefer using a good microphon (have two Shure mikes). But for a quick narration I often use a Plantronics professional headset, from the type used in call centers. A lot depends on your voice of course and of the environment. You can put the mike in a ‘box’ that will shut out environment noises, not so easy with a headset. Same with using a pop filter. Even with my microphons I always give the audio clips a quick edit using Aution.