I have sent an email, but I believe the price will be mindblowing, and, really, how often do I play the 6-stringers I have? Because they have essentially the feel of a baritone guitar, they demand a totally different approach in playing them. Much lighter attack and such. I would probably have to sit down with one for a couple of weeks to break it in (or, more correctly, have it break me in!).
That neck doesn't look like a short scale one to me, but the comparison with a regular EB-2 has me doubting now ... If it's just a short scale 6 string, then in essence the only dif to a reg EB-6 is a second pup (though I'm not entirely sure whether some EB-6s did not creep out with an additional bridge pup, it probably wasn't too dificult to ask for one at the time).
If this thing is long (or even medium) scale, then it's another world wonder. I asked in my email to the seller. And no, Dave, I wasn't aware of its existence.
The Elvis connection - though I like Elvis - means nothing to me (I wouldn't pay more for a Ritchie Blackmore pre-owned bass either). I saw his 4-/6-string EB doubleneck bass (i.e. both halves are basses!) exhibited at Graceland though, that think looked impressive in real life.