Sounds like a neat idea.
But prices can fluxuate, so i wouldnt need to store my own price history, i just check the search funtion for what i want to sell to see what other people are selling it for.
Just like in FFXI.

Like many of the other posts about retainers, our system is a lot like the AH already. Just a 3D AH, that you get to go into and locate your purchases.

FFXI was the text based AH.
FFXIV is the future! ;p