I like the idea and think it has enough merit to be looked into. It is an issue that has been around for a long time and seems quite difficult to correct. There may be concerns from Staff, but hopefully you can work with them to find an acceptable solution.
For me, the biggest hinderance at the moment is the sellers themselves. After an auction has ended, many go back and remove the image of what they were selling, any detail about it, and rename the threat title to Sold or Closed. This making doing research on accurate pricing very difficult, especially for Pokemon and Items that have significant rarity.
Ideally, there would be a rule in which players would need to leave that information in place, only allowed to edit to mention the item has been sold or removed. This would make price checking significantly easier and more accurate. However, that would require even more work for the Trade Mods (the last thing they need), as it would be another rule players would probably constantly violate, so I understand why it's not realistic. A project like this wouldn't fully solve the problem but would help put us in the right direction.