It's not just music, it seems the complaints about "too expensive" turn up anywhere something is downloadable.
For example, I know a small software company that make niche-genre games. People will happily pay £24 for the PC downloadable version, but the port to iPad, which contains everything the PC package does (including multi-player and the same AI as the PC version in single-player) which sells at around £8 or £9 attracts the complaints of "too expensive, ipad apps are cheap and throwaway and should only cost a couple of pounds at most".
There have always been complaints in the UK about CD prices as well. While there is some justification in that UK prices, ignoring taxes, worked out higher than US and even other European prices. As did (and do) a lot of things. Which is pne reason why we were known as "treasure island" by certain far-eastern companies. But the complaints mostly consisted of "a CD costs 50pence, how come I pay £15 for an audio CD? It's a rip-off, should be a couple of quid".
That the audio CD is well-packaged, professionally made and recorded, royalties-paying and any given artist can only produce so much work so needs a decent return on what they do all being ignored. No different to assuming the price of a gig ticket, including even the VAT, goes entirely into the artist's already over-full personal bank account when complaining about paying £20 to see a band.
My personal gripe for many years was the price of Fender, Gibson and Martin instruments and amps in the UK compared to the US. And that Fender US customers got a case included while UK customers were expected to pay another £40-£100 for the same case. To be fair, it seems the import agents of the time (and some retailers) were responsible for some of that, but it wasn't half annoying.