Just thinking about it, 'cause it's kinda interesting, is that "high-end" really depends on context, whether it's high-end because of value, or high-end because of performance, or simply high-end because of the reliability and renown of the manufacturers. Personally, I see "high-end" as a performance thing, since we're talking about computers here and performance is a key aspect of it all; if I bought an nVidia 680 card for £1, it'd still be a high-end card by way of performance and common price.
Lets say there's a quad-core and a dual-core, now lets say they both perform above 60FPS on the maximum details within games, now lets say they have the same cost, but the 4 core CPU can perform a little bit further than the highest FPS limits of the latter CPU; which CPU is high-end? To me, I would see them BOTH as high-end, since they BOTH perform to today's high standards.. but, then, even that changes so rapidly, as our standards are constantly changing with the speedy jumps in technology. I'm going around in circles, aren't I? :P
I say my rig is high-end for various reasons (with perhaps the exception of the graphics card as new games have tipped the scales against the favor of the 550Ti) such as the cost being substantial - worth a fair bit over £1k in-store. The performance of the rig, since it floors almost every game (except the aforementioned new games) at maximum details; that said, HD seems to be the "it thing" ATM and I don't need or care for it, as I run 1600x900 and it looks lush. When I've fitted my two new ASUS 560Ti ToC cards in SLI mode, I will absolutely declare it very much high-end.
So what do you see "high-end" as? Do you primarily see it as the cost of an item, the performance of an item, or the positive renown and reliability of an item?