One should expect more costly gear to offer an improvement but there is no rule that says a positive change need cost more. Better to just focus on getting the fundamentals right and see where that takes you.
cost of improvement
Of course there are exceptions to this, but in general, does one usually have to spend twice the amount of the previous item to actually notice a tangible improvement? (Provided the equipment hasn't reached the law of diminishing returns). For example the difference between a $500 set of speakers or amp might not be a noticeable difference from a $650 set of speakers or amp. But by the time one jumps from that $500 price point to the $1000 point, does the improvement become apparent? My question is does it usually cost (1.5 times) (2 times) (4 times)? as much to reach each "next level" of component improvement until the law of diminishing returns sets in.