whether it's accurate or not, I have found a lot of Ebay sellers use the SMR to set their prices. Just look at some of the usual suspects that put overpriced BIN's on that never seem to sell. The hilarious thing is seeing card shop owners use the SMR to price ungraded cards.
In the end there are no accurate price guides. Any card is only worth what you the buyer are willing to pay for it. If a dealer really wants to sell a card they should be willing to sell it for what the "book" value is. Hardly ever happens. I spent last night making offers and counter offers to 2 sellers, and in the end they were still arguing with me over a measly $2 difference between my offer and theirs. They are fine with using a Beckett or SMR when they price their cards, but try getting them to use one when you are buying

oh and try telling one of these blowhards that the Beckett is only a "guide". they will laugh you out of the room !