TCDB pricing takes the median (middle) value of the five most recent prices. Anything older than the fifth-oldest price is not part of the calculation for the price shown under a card. It remains visible for historical purposes when one goes into the pricing information for a particular card. If less than five prices are available, then yes, some older prices will be used and could possibly not be an accurate representation of the actual going rate of a particular card.
Shipping prices are not used to calculate said median value. They are added for context when viewing the sales data for a card.
Prices submitted are expected to be actual sold prices. SportLots has a minimum selling price of $0.20 per card (formerly $0.18). This means that a card that has a price submitted by SportLots of $0.20 actually sold for $0.20. Mistakes can happen with that information, just as mistakes can happen when a user submits a price, or a scan, or a checklist.
It is worth noting for everyone that TCDB is not intended to be a price guide. The value field is meant to increase the relevant details and information available for a card and associated set, just like the comment field, Note/Note2 fields, and Trivia sections. Those who choose to use the pricing available for their own purposes can do so. If you need an absolute hard and fast price to value your cards, I am afraid you will struggle to find that anywhere. Some discretion should be used when it comes to prices; not only here, but in any market place.
There are several dedicated members on this site who work hard to ensure the pricing function of the site is operating as best as it can. Discrediting the pricing as an absolute waste of time or calling for its removal is a disservice to them. If you don't like it, don't use it. I commend those members who work closely within this area of the site for their civility during this thread (and all other pricing threads that come up every six months).
FAQ regarding all facets of pricing is here, for those who may want to use it for a reference.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.