Hi Rory,
I think Steve gives a very informed description of the tradeshow, I work for a loudspeaker manufacturer and have attended these shows for years now. They are very expensive to undertake from an exhibitors point of view when combining the cost of floor space and factor in the Hotels and Restaurants taking full advantage of a captive market with inflated prices.
However Frankfurt Messe and Namm are both good shows, Frankfurt being the larger of the two catering for all aspects of the audio industry including sound reinforcement, lighting, traditional instruments and so on.... it's huge
Namm is mainly a music retail and recording based show catering for the American market or visiting international distributors, with a larger representation of the exotic instrument and amplification manufacturers. From a bass point of view the likes of Fodera, Sadowsky, Alleva Coppollo, Mike Lull, Zon, Modulus and so on.... you won't see those guys at Frankfurt. Endorsing artists also make a point of being around. If you were considering visiting Namm make sure you pre register as security there this year was strict to combat the sale or the exchanging of passes.
My advice would be to look at the list of exhibitors or people you would like to see, there always published on the websites. Call them and see if it's possible to make an appointment at the show or get the name of someone you could talk to, but don't be disheartened if people are easily distracted by dealers or distributors turning up mid pitch. Good luck.
Mick