The quality of microphones ranges all over the place, and price is not always an indicator. Before buying be sure to check the specs for the frequency range of what the mic can reproduce if the sound quality matters to you. You should be able to find a graph in the technical specs. Plus or minus 3dBa is the normal signal strength range that is used to determine the frequency range covered. Many mics only effectively cover part of the normal range of the human voice, similar to using a land line phone. Also is worthwhile to look at the pattern of the mic, shotgun cardiod etc, and make sure that the coverage is going to be broad enough for your application. It doesn't sound pleasant when the subject you are recording is moving in and out of the effective coverage area, unless you are going for the fading in and out style.