No it doesn't work that way.... pre-ordering something is usually done for the same price... even if you have to wait a long time... I paid exactly the same for my Black Ops II as someone who buys it in the store today.... Same goes for iPads, iPhones etc.... Sometimes you even pay more on pre-order than when it becomes readily available because of the exclusivity to have something first.
It worked that way for every game I was interested in. (And usually opted not to pre-order, since the discount didn't justify the risk of buying before trying a demo.) Alternatively, bonus items are often given to preorderers, still making the eventual value of what you receive greater than what you paid.
Exclusivity is a bit more intangible and I don't presume to model the incentive structure of iPad preorderers. But I can certainly model the incentive structure of people who order mining devices. Excluding trade friction, a single available immediately will trade in the secondary market for more than what it costs to order a single to be delivered in a month; the difference will be roughly equal to the profit it can generate in this month.