I just looked at the pics on eBay and I don't think there is any worry about them being genuine. The point is that they were advertised as good to very good and they are that. The Redbook I have (albeit a few years old), doesn't even price below very fine, so that is no help if you are going to buy Washington quarters in the lower grades. The prices you quote are for grades considerably higher than what you bought. Keep in mind that there is seldom a linear scale for price vs. grade. Typically, the scale is more like exponential - higher grades bring considerably higher prices than lower grades. Supply and demand.
Back to answering your question. A Redbook is a prime reference book to own and if you just can own one reference, this is the one. Redbook prices are not terribly far off from what you should expect to pay. But, as Don points out, there are online sources that may be more up to date. Since the Redbook is an annual publication with only one snapshot of values taken months before it goes to press (note that the 2009 Redbook has been available for some time), in these times of market fluctuations, don't count on values being accurate.
John in ID