I think you have nailed the biggest problem with the public pricing. It would take a large team of members monitoring the internet for sales of cards so as to continue inputting the prices into the database to make it somewhat accurate, and that is a very soft somewhat.
To make it easier, maybe if those adding prices concentrated only on cards that are recognized as not being commons, more relevant prices could be maintained but even then, the amount of cards that this would still involve is huge.
I think most have resolved that there are enough pricing sources available (mostly all available online and not always needing to be paid for to get access like Becketts does), that the pricing mechanism here is too small of a sample to make it useful. As others have pointed out, regional card prices are affected by the fan base. The few that are reported here are affected by too many of similar factors.
As for making it a personal-use feature, AGAIN, using the Detailed Add feature, one can enter the price he paid for his own use in tracking his "investment".
Bruno
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Check my Profile page to see my 2023 Goals and my Lists of sets near completion (5 cards or less) or sets getting close (less than 100 cards missing and 75% complete).
https://www.tcdb.com/Forum.cfm/Page/B/ID/0/?MODE=VIEW&ThreadID=25745&C=0