In my opinion, every dealer who doesnt show up with a little mix of everything is only hurting themselves.
[MENTION=4788]Kennesawsportscards[/MENTION] , your issue is your dealers that are complaining not the discount box guys. People collect what they want regardless. Like it was already mentioned, the guys who are at the bargain tables are most likely not shopping for the cards the other guys have. Sure sometimes there is overlap but they're two different collectors. And if you have a lack of people spending money at the other guys tables its most likely because A. the declining interest in the hobby B. the seller (like mentioned before) has the same old cards every show. C. Are ridiciously priced.
Dont think one type of customer doesnt show up because some dealers dont have what theyre looking for. If sellers are complaining theyre not making money, they need to first look at themselves because the problem most likely lies with them.
If a collector wants a mid-high end card they can go on ebay most days of the week and buy those same cards well under what crazy show sellers are trying to move them at. On the flip side, those that like the low end cards for whatever reason, be it team sets, fill set needs, etc they prefer the shows because they dont have to pay $3 shipping on every card they buy.