I agree there are big name roasters charging a fortune for mediocre coffee but I think you have to factor expertise and heritage into some pricing. Promotion costs these days are also fairly relative regardless of location given the power of social media for spreading the word at no cost.
Purely out of coincidence I lived round the corner from three roasters as they started and grew in London. Square Mile, then Dark Arts, then the London roastery outpost of AllPress.
I’d buy beans from Dark Arts in 2014-15 when it was literally one dude roasting a PNG on a fairly small Diedrich in a railway arch. It wasn’t bad, but over time their relationships with farmers grew, their staff grew and visited some of the farms etc and now their offerings are really solid and diverse.
AllPress started in like 1990 in Melbourne so again brings huge heritage and experience growing among arguably the biggest third wave scene.
Ozone is another one that has an exceptionally high level of knowledge of coffee in general and as a result produces expensive, but very good coffee.
I’m not saying they’re all bad but I think you’ve gotta expect to pay a premium when it’s not ‘some guy bored with his day job in BFN who had great coffee once and bought a roaster’. There are a lot of businesses shipping high volumes of really average coffee.
You can indeed get great coffee for £10 a kg just as you can get awful coffee got £40 a kilo but of all the commodities I think coffee can often be one where the price is reflective of the quality you’re getting.