Well I have two Lemond(Trek) carbon fibre bikes from the last year they were made. One is Shimano 105 level and the other is Ultegra level. I bought one new for $2K and the other one year old for $1K. They aren't custom bikes but they are full carbon and are dreams to ride.

I think the most expensive carbon fibre bike I've seen in the stores is about $6.5K. Custom is a Katy Bar The Door price.

This recumbent is custom so maybe that isn't out of line even though it certainly is out of my affordability range.