Difficult. There is no linear relationship between cost vs. quality; cost vs. enjoyment sometimes moves in the "other" direction, and there are complex interactions / dependencies among components of a system.
We each arrive at our internal sense of what is a lot vs. a little for a given component type after experimentation. Then it changes over time. Are you counting MSRP, or willing to explore used markets (better)?
In my present incarnation I’ll splurge most on amp, splashing 20K+ (used) for a big-ass VAC tube amp. I don’t know how to get that sound for less $ yet. I’ve also been equally happy with "just" $2K - $4K tube preamps and phono stages (used), but I’m still quite choosy about its flavor of sound from model to model. For speakers, Tannoys in the $5K - 15K range (used) make me pretty happy. Cables I’ll still splash out a few K for silver speaker cables & interconnects, but I generally care a whole lot less about power & tweaks these days - to the point of almost ignoring them.
Room acoustics has minimal focus. With the controlled dispersion of Tannoys and my seating distance, the room is much less of a factor (with proper setup). I care a whole lot more about "satisfying" bass than accurate bass, which makes things a lot easier too.
