If a dealer drops the price when it is still a preorder item, he/she should extend it to all previous preorders as well. Not doing so, the dealer alienates his customer base and hurts himself/herself in the long run. It's common business sense. But this is up to the individual...
Part of the dilemma from the dealer (importer's) perspective is that
dealers usually have to estimate what qty to import. This usually happens right when the product's price and release date is annouced and we're needing to commit a number with our distributor. We're talking a several months with no preorder confirmed....
If one doesn't reserve enough in advance, you are left with no stock and no making a profit. You store gets less foot traffic when you don't have the right items in hand. However, if you overorder, you could possibly screw yourself in loosing quite a bit of money. It's a constant pickle toy dealers had to handle.
Take for example the Toynami Clear Morphers (Xstoys - Tony always likes to bring up this sore subject with me) that came out a few years ago. I figured they would be quite cool to resell so I bought 30 sets at the SD Con. I still have about 24 sets sitting around collecting dust that I can't even unload at a loss of $20.00 per set.
Conversely, I should have saved more Low Viz and Hikaru 1S to keep in my personal stock. I had quite a few cases of each at one point but sold them at no more than $140 a pop...
Hmmm...now if I sold 200 GBP-1S like in your example Haterist, I'd be smiling!!! Unfortunatley, I am a one man show and don't even get that type of throughput.