A bit of both ....
I went to Paducah one year and specifically wanted a large cutting mat, the "clear" type. Got a good deal on one made by Beba.
I also went with a shopping trip to Hancock's of Paducah high on my list as I heard the sales were to die for (and they were!).
I went to DesMoines another year specifically to see the Egyptian quilters and their quilts, and hopefully purchase one. I bought TWO!!
All the other shows I went to (as well as the two above), I also made purchases of things that just caught my fancy. With the exception of purchasing the fabric in Paducah at Hancocks and other shops outside of the "show", I don't buy cotton quilting fabric at the vendors in the show. I've not seen prices that are any cheaper than I can get at my LQS.