I owned one of the original Dartzeel NHB pre amps which I bought 2nd hand, it was about 4yrs old with the built in phono. I was going to get it upgraded to V2 or trade it in for a new one but there was a very long wait time, due to part shortages apparently, so went another route.
In the UK the preamp was around 15k GBP when it came out around 2004/5. Within a few years it went up to approx 24K due to the weakness of the pound. According to the bank of England’s inflation calculator 24K (in 2008) would be 38k in todays money. Even allowing for some improvement costs the current a price tag of 54k is a very large increase, needless to say it puts the amp in the ultra expensive category.
In 2008 the cost of the Dart NHB was equal to the average annual income in the UK (24k). Average income is currently around 30/4k so about 60% of a new Dartzeel. No wonder they are not flying off the shelf in spite of being an excellent amp!