I think that paying to get help to find the right "off the shelf" bike for customers would be great since custom bikes cost so much.
However, I think that as a customer, I would want to know approximately how many hours it would take you to help me find the right bike for me after analyzing all the data. Some of the bike fitters than I know also does what Catrin mentioned above....paying around $250/$300 one time to find the right bike for me, fit me on the bike that I bought, and a followup fitting one to two months later. However, the fitters that I know do NOT do lifetime fittings, even if it is the same bike. Catrin's fitter is a downright steal for lifetime fittings.
2014 Liv Lust
2013 Specialized Fate Expert with carbon wheelset (sold)
2012 Specialized Amira Elite
2010 Santa Cruz Juliana with R kit and Crampon pedals (sold)
2011 Specialized Ariel Sport,suspension post,Serfas Rx Women's Microfiber saddle (sold)