I don't want to say what you have heard a million times already but the bottom line is: You get what you pay for!
If you want to read on about my experience:
Transient response is the biggest and most obvious difference between these lavs vs the DPA (how clean and clear the overall signal is). The bass response is much better (maybe too good, it picks up EVERYTHING...during a serious rock show, it will really be overwhelming but not a lost cause). The other lavs you speak of are much bigger (gotta stick them under a hat or else look funny with the caps sitting noticably clipped to your hat). AT853 omni I have played with indoor (Showbox, Seattle) with the most horrible results...it had the nastiest bass thump during a Supergrass show I taped, with the DPAs I never had an issue with the bass thump (I always use my Sonosax with those mics, so it wasn't a mic-pre issue). I have used the card caps with the ATs and produced nice sounding tapes. I like the DPAs much much more tho, now I actually listen to the shows I have recorded with them! The ATs have a characteristic sound to them, a 'tinny' sound as some people say. The MKEs, I think are really similar to the Soundman OKMs...they are not as 'tinny', IMHO....but they lack the brightness of the ATs and DPAs. If stealthing is your gig, DPAs are hard to beat. My starter rig was a Core Sound Binaural > Batt box > M1, after that AT853 > Sonosax > M1, and currently I run a DPA4061 > Sonosax > modSBM > NJB3. So I can say with reasonable confidence that the DPAs are totally worth the cost.
I cannot explain why DPA uses a two wire coax vs the three wire like the rest of those guys, maybe due to the thiness and minanturzied assembly?
If you hang out for a bit, you can get a used pair for about $550-750 right here in the yard sale section, definitely worth it. Be careful of those being sold on ebay for a song, they usually have been to Mars and back.
ANDY