but the chance of they coming down in price is less in the beginning rather than end of the show depending on how much they sold..what do you think?
National and/or specialty dealers are unlikely to lower their prices on 2nd or 3rd days of a show; they know they'll have fresh clientele at the the next show in a week or two. This approach might work with smaller local dealers.
With specialty material, cost is likely far less of an issue than availability. If you're filling spaces in a standard album, this is likely not an issue, but if you collect anything esoteric or unusual, then simply finding the material is the challenge. Over time you learn which dealers are likely to have (or even possibly might have) certain specialty material, and in those cases it is important to hit them right out of the gate.
If what you were looking for has already been sold, it doesn't matter how cheap or expensive it might have been. The point is moot.
The dynamics are different when you focus on material that isn't mainstream vs. fill-the-spot-in-the-album collecting (and I say that without criticism; there are certain countries I collect in that manner). As a general rule, garden-variety Scott-listed material can be had from numerous dealers at any given show . I can have my choice of dollar value Columbians, Zep sets, and other "rare" items (tongue planted firmly in cheek) from numerous dealers at any major show; all it takes is money. Finding truly scarce material, on the other hand, the cost isn't issue (and frequently the scarcity and cost do not correlate if the material is outside the mainstream); you just have to know whom to hit up, and even then you might strike out.