Thank you for the kind words - they describe exactly what we're trying to achieve here.
A little addition:
Coins, like any other artistic investment, appreciate and depreciate according to demand as much as anything else. For that reason, it's tough to create an accurate database of values - what's correct this month might be off-kilter next month due to a gain in "perceived value" among collectors. A favorable news story might come out about an American Eagle, and there'll be a bump in demand (hence price) as a result. The recent USS Republic coin recovery is a good example. Some really, really nice, rare coins are hitting the market as a result, some of which will affect the populations of certain high-end rarities. You would think that the sudden addition of coins at the high end of a group would drive prices downwards (more available means cheaper prices in economics), but I contend that they will drive prices upwards. The publicity surrounding the wreck recovery has increased the size of the audience for these coins and added a category to potential collectors of them - people who collect shipwreck coins - and as a result I expect prices of similar coins to substantially increase over the next few months.
Words of caution about online auction sites: There is always the possibility that competition between two or more bidders for whom a given coin is more important could drive the price artificially high. For instance, two people who need the single coin to finish a collection will likely be a lot more enthusiastic about bidding than simple supply and demand might indicate. You'll see this often in Heritage records.
ebay is even worse, because of the addition of bidders who aren't really aware of the true value of what they're bidding on. I hate to see it, because it hurts the bidder's pocket, but people will bid moon money for lesser coins simply because they've somehow become wrongly convinced that the value is greater than it really is. Then you have auction fever, the spirit of the competition pushing bidding to unrealistic levels.
Especially with
ebay, certain categories tend to return unrealistic results. Higher-end coins (those worth, say, $500 and up) tend to be either underbid (knowledgeable collectors tend to stay away from
ebay for coins of this value, knowing the prevalence of uneducated bidders) or overbid (uneducated bidders FTW!

). Lots of cull coins can be greatly overbid as well.
When researching auction results, look for widely varying prices for what seem to be similar coins. That's a sure sign of unrealistic pricing due to bidder activity. A one- or two-coin spike might be the result of the coin being a variety of greater value, but consistently-varying results indicate you should proceed with caution.
The point of my long-windedness is to make you realize that "pricing guides" are kinda difficult because it's a moving target, subject to the whims of the collector, rather than reality.