Ok, I'll take up the mantle. (Belated) welcome to the site. I'm glad you're enjoying it, but not at all surprised. To you question: you've hit upon probably the least reliable thing about the site, but there's little help for it. The site is not meant to be a pricing guide. The prices here are sometimes wildly inaccurate for many reasons. If I have a 1953 Paige, it could be PSA 8 or PSA 1 or ungraded -- the price listed on the site will not take that into account. Perhaps all three prices are entered. It will give the mean price. Which tells you almost nothing of the value of your PSA 4. So it's just not that useful.
Prices here are entered by members. Just click on the card and explore. You'll see an option to add a price. I strongly recommend, beg really, that you only add prices that you are personally aware of, and that you add as much info about the card as possible. That way, at least someone might get some use of the information.
See the other thread going now for more information. Or browse old threads. This comes up only slightly less than the debate about graded cards....
Good luck. Enjoy.
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