My bass is a Kolstein busetto travel bass, but it's not an EUB it is a fully carved acoustic instrument with a downsized body. I would never even consider it in the EUB category.
I happen to live close to the Kolstein shop, my bass does not have a removable neck, it did not need to be shipped to me nor did I need the travel trunk. I've owned it since 2011 and the price was WELL under 5k. I don't know the current prices.
I just brought a Kolstein Busetto Travel Bass and played my first gig in a library. I played using the planet wing pickup through an Acoustic image Ten2. I previously played an Eminence 5 string EUB for about two years because of the toll the last two winters had on my carved bass. I love the acoustic tone of the Busetto bass, its very inspirational compared to the Eminence. Right from the start of the concert I was in trouble, i use an K&K preamp on the stand to adjust the settings btw the bow and pizzicato and could not dial in my sound. I thought the battery was going on me as I had the gain up on the pre-amp and the amp. I got a better sound as i concentrated on the low end and i managed to start to enjoy the bass. here are some of my first observations.
1. The Planet Wing pickup sounds very good on the E&A but then it starts losing the volume on the D&G dramatically
2. The difference btw an Eminence and this bass is in the attack. People always complemented me on the sound of the Eminence because it filled the room but it was always like playing an electric bass. The Kolstein Busetto bass attack is a swell/mwah sound like a really good 15k+ bass and i have to adjust my playing style in the future.
3. I was also toying with the idea of putting another wing pickup for the D&G strings....an experience out there
I have to work on my settings. I definitely have to figure out why the preamp volume had to be so high as the piezo sound gets too thin and tinny.
, sealed without a tweeter. It opened up my ears to what tubes can do to warm up the piezo, 
Mem’ries, light the corners of my mind...