Cost

[newbie]

Why do I have to pay more than the price guides for certain coins?

[J.Cordeiro]

That is a very good question. Picture this: (THIS IS JUST AN EXAMPLE) you sell coins for a living. You are trying to sell a coin that you bought for $10.00. Its book value is $10.00. Shipping and handling cost $2.00. Placing the advertisement to sell the coin cost another $1.25.
That coin now must sell for $13.25 just to break even. Breaking even does not pay the bills. You must generate a profit if you are going to stay in business. Now the coin must sell for $15.00 so you can afford to buy more coins, mailing supplies and cover the cost of over-head.
Another reason is that the market will allow for greater prices. If you have two people who REALLY want that coin and start a bidding war, the bids can go way over book value. The true monetary value of a coin is not what you can buy it for, but for what you can sell it for.
Also, there are many people, from businesses to individual persons that are dishonest and will try to jack up the prices and sell to unsuspecting customers.
Those are just some of many reasons.

[danglen]

It has been my experience that catalogs and price sheets are merely a guide, and not always in tune with what the market is really doing. Most books are written (and prices listed) a year or two before they actually become available. This is the reason that the 2008 Red Book is already available in book stores. Otherwise, the publication would have a very short life span, because who wants to buy a 2008 price guide in 2009? Another factor is that a lot of these catalogs and price sheets get their prices from completed auctions, which generally present better material, so the pricing on lower grade material is nowhere near the actual market value. I have found this to be especially true when it comes to currency valuations.

[J.Cordeiro]

One pretty good way of finding out the market value (my opinion) of a coin is to log onto e-bay and look up a coin simmilar to the one you are thinking of buying / selling. That, in most cases, will give you a pretty good idea of what people are willing to pay for that type of coin.