You can definitely get a humbucker for under 600.........lots of sets on ebay and if you talk with the seller you can probably bet the entire set for between 700 and 900. I waited and waited for each set to come up at very good prices. I think I got my tele set for maybe 600....my strat and humbucker sets were somewhere between 700 and 900 for each complete set.
The one guy in these parts best known for rock and roll and and all around master of the guitar continues to praise them and according to his ear, they are the best pups he's ever heard..... Of course he may be biased because he is the same guy I turn to to assemble all of my Warmoth kits/sets/projects. But he's had maybe 250 guitars (sometimes he may own a guitar for just a month)......but at age 53 and with 43 of those years playing serious guitar, the Zephs are the best he's heard. I've played for almost the same amount of time but no where at his level. I have lots of guitars but have not owned even a fraction of what he has.............but for what it's worth, still, and with all those who use my guitars, the Zephs win. HD isn't for everyone and neither is the real price range (much less than most probably believe), but they are preferred enough so that anyone checking them out has little trouble concluding they are a step up. Have no idea about heavy metal and other hot pup comparisons.... They are super clean!