Anchoring bias
This is the main reason for the 15k bikes (or the 100k cars). If the magazine (or shop, podcast, youtuber, etc.) tests a 10k bike, automatically our brain re-adjust expectations and the 2k bike is "budget", "affordable" or whatever. There is also the reputational part of course, "if brand XYZ can make a 10k bike, I'm sure the 2k bike will be great too!".
I think that is the main issue when people say today's bikes are expensive. As
@clubby mentions, bikes back then were similarly expensive. Today we get much more bike for the same money (mostly because now everything comes from China while before a good chunk was made locally or in countries like Japan or Taiwan where people get a fair pay and labour rights, so basically workers and the environment pay the differrence).
But what has changed are the expectations. XT was top of the range, the stuff racers used, totally aspirational, most of my friends had 200 GS bikes, I spent all my childhood money to get Deore LX!! Now XT is the standard, the benchmark. If you go to SLX, or 105 on road, you are being "budget conscious". What happens to all the other 8 gruppos down the line!? For cycling "experts", it seems there should be just 3 groups, XTR for racers, XT for everybody else, and Tourney for BSOs...
I don't agree that bikes back then changed a lot y-o-y though. Excluding the suspension ones, that were starting to be developed and obviously designs were changing by the day, everything else was pretty much the same. Many brands would have a couple of frame quality levels, and then mount whatever Shimano had at each price point. The following year they would get a new colour, or at most the usual trickle down from Shimano (Deore LX is now Exage, DX becomes LX, and so on... There was the Hardrock, Hardrock sport, Hardrock comp, Hardrock whatever,...
This graph from the LinkedIN article is very telling. Bike numbers go up or down, but the number of participants remain constant. We, the already convinced, are the ones moving the industry. If there is internal cable routing, press fit BBs, or whatever standard you don't like, it is because enough of us are buying it (or not and then threaded BBs come back ;-)).