Sometimes this is simply because one reseller is taking a larger profit margin than another, but often it is due to a process called deal registration that happens between the reseller and the hardware vendor. Deal registration is supposed to be a mechanism that rewards a reseller for the time and resources it invests in trying to sell you that vendor's hardware. When guaranteed a better cost basis, the reseller can better justify spending the time necessary to give you a quality proposal, since it knows other resellers who haven't invested in that work won't be able to compete on price with them. So this is normally a net benefit to you as the customer.
One the other hand, when many resellers scramble to register you as a customer at the same time, some unfortunate results may follow. The worst case is when a reseller with little technical knowledge of the product registers you and prevents other vendors who do understand the technology from matching the price. This may result in you receiving one very poorly constructed proposal with a low price, but glaring design deficiencies -- while other, carefully crafted proposals are saddled with much higher hardware and software pricing.
Depending upon the vendor in question, there may not be much you can do about this. But most hardware vendors will honor your request to vacate a registration from a reseller that hasn't actually done its homework and given you a good proposal -- freeing you to get both good pricing and a partner you trust.
This article, "Building a better storage RFP," originally appeared at InfoWorld.com. Read more of Matt Prigge's Information Overload blog and follow the latest developments in storage at InfoWorld.com.