@Budler covered a lot of the relevant points re Sportlots.
I will add the following with regard to shipping which may explain why it is not listed/impractical to list with Sportlot pricing. I imagine very few cards are single card purchases through their site. I doubt many buy a card for .20c then pay the seller's $4 (or whatever) shipping price. Most of these purchases would be for multiple cards, so then how do we breakdown/assign this shipping cost on a per card basis? I know this shipping conundrum has been debated before and doesn't need to be rehashed now.
As.an international buyer I take advantage of Sportlots box shipping option - sellers ship once a week/fortnight direct to Sportlots who store the cards until ready to be shipped out to the buyer. This way the seller can ship multiple orders in one package allowing some sellers to offer free box shipping. Thus, some of these cards can be a true purchase price of what is shown with no additional shipping.
However, keep in mind, whether a shipping cost is entered or not, it is bot used to calculate the median price as displayed on the card's page.
As @Budler mentioned, I have also stopped entering my Sportlots purchases to the site. From my experience the sales data is not pulled across instantly and usually takes a few days/week for it to appear. I'm not sure if there is say a once weekly mass migration of data, but it is certainly not performed in real time as individual sales occur.
To touch back on the Brady issue, with the caveat I am not a football fan, or know anything at all about the card market. What I do know is he was a late draft pick (199th?) and did not play his first year. In his second season he took over starting after Bledsloe got hurt and stayed starter amid some "controversy" the following season, however didn't really break out until his 4th? season. I could see a 199th pick who is not playing have his cards selling for low amounts at this stage.
I think Sportlots offers a valuable balance against some of the prices loaded here for cards that have one off user loaded prices, with no corroborating evidence, that are unrealistically high.
Having said that, I agree there are limitations to the pricing. The lack of shipping is one, but also the lack of card condition. A chewed up card is obviously going to sell for less than a better condition one, but we don't have that information recorded for Sportlots sales.
What I do find remarkable is that we now have access to a pricing history that dates back to the early 2000s. It impresses me that Sportlots has been around 20+ years and has data that can be supplied. I think, if people could open their minds a little and stop focusing on the minutiae, they would really this is an incredibly valuable addition to the history of these cards.