I am a Travel Agent and the sites always list the fares before taxes and fees. Those are all added once you click purchase and then they will also add a service fee just because your using their site.
Not all of them do. The ones I am looking at list fares, extras and totals right off the bat. Also it is obvious that many of them are either ‘the same’ company or they use the same software such as ITA because they present their results in the same format. One thing is CERTAIN - many of them present very different total $ answers for exactly the same flights - possibly their fees that you mentioned.