the very fact that a lot of stimulant abusers are whistling so annoyingly loud and you get under-age girls yelling uncontrollably and so forth only adds to the fact that you need a very good sound system to cover that racket. Also, like asylum said, there are plenty attending purely for the musical experience - hearing your favourite and unknown tracks played so loud on a quality sound system which is at a different level to the one at home.
£30 is a lot of money because those events you listed are national teams or worldwide celebrities/singers known by the vast majority around the globe. the prices are still disgracefully high, but you cannot compare a helter skelter event to a sport or other concert. £30 is a rip off. just like the football is a rip off and other things. it's the worst argument to simply measure oneself by comparing themselves to another.
sound quality is very important... do you not have any crap sound recordings of sets which mean you cant stand hearing them? plenty i had in the car that sounded terrible, so i threw them away. it affected my enjoyment of the music.
for those in the main room, the sound quality is normally amazing or if there is some DnB room, the quality is clear even though the music is commercialised shite. they always cut corners with techno music. all the big promoters are terrible in this respect. as long as the majority are happy, they will continue to put out a mediocre event.
it would be interesting to see how many continued going if they did not take stimulants which, let's say, affected their judgement.