Here's a typical HC bike.
The frame is the Sam Hillborne from Rivendell (frameset MSRP is $1000), and the parts are mostly mid-level Shimano (Deore, LX Tiagra, etc) and similar mid-range parts from other brands, bringing the total price of this bike to around $2100. None of the componentry on this bike is the kind of thing that bike geeks lust after, but none of it is shoddy either. This is sort of the sweet spot of bike part economy, where you get most of the performance (whatever that means to you) at a fraction of the price of the flagship groups and boutique brands. Don't get me wrong, we like fancy parts, too. If somebody wants a $3500 Sam Hillborne, we are happy to accommodate!
People who are interested in bikes tend to be knowledgeable about the price hierarchies of, say, Shimano groups. The very existence of the hierarchy creates aspiration for the upper-echelon groups, even though most of us can't accurately articulate why Dura-Ace is so many dollars better than Ultegra is better than 105 is better than Tiagra, etc. I once worked at a larger shop, where we carried some big lines that featured similar bikes at various price-points. We had the mid-range 105 bike that met a popular price target, but I never let anybody just buy that bike without at least trying the Ultegra bike that was, say $300-500 more. After riding the more expensive bike, most claimed, without any prodding from me, to detect an infinitesimal improvement in shifting smoothness or some other mechanical attribute, and often that was enough to justify the expense of the upgrade.
That was some easy up-selling! Why was it so easy? I'm no marketing scholar or psychologist, but I believe the answer lies in our fear of buying something cheap, then regretting it later when the cheap item continues to disappoint long after the cash savings has been forgotten. Playing the "regret avoidance" card has been part of marketing and sales strategies forever, and it really works.
Luckily for us (cyclists), we are living in a time when even the relatively inexpensive stuff is really good! There is nothing to regret with a Deore derailleur or Tiagra hubs. They do the job, look fine, and tend to last a long time. Sure, if you have the money to spend, and aren't concerned by the diminishing returns of expensive parts, there's nothing wrong with going top-shelf. Just that you don't have to, if your goal is simply to have a nice bike to ride.