Passes aren't that hard to come by if you have a connection or three within the industry. Passes are available to companies or individuals who are registered with NAMM so you get staff from manufacturers, endorsing artists, retailers and media. Companies are given an allocation of "guest passes", which seemed to be a lot of the crowd there today who were there for autograph signings and to grab photos with a few stars. It's fairly controlled with ID checks upon entry.
As for sales, a lot of the bigger manufacturers (e.g. Ibanez, Fender, Gibson) don't appear to sell anything at these shows, but the more boutique manufacturers such as Spector and MTD had already sold a lot of their instruments but the time I got there this morning (folks can pick up the instrument at the end of the show on Sunday). I wasn't there as a buyer, so can't say if it's considerably cheaper to purchase at the show or not. I have heard that some vendors will cut good deals on Sunday to avoid having to ship the instruments back with them.
