as you stated it just seems like too much work and really for only an estimate
if anything was added close to this it should be the simple "starting at x on the market"
or something along those lines

also, as you know, many people trade items as bulk, or as duels/prizes
so keeping a tab on trading and street price would be really hard and genuinely confusing using only code
the only sure fire way to get an estimate is to have some sort of human marketeer to regularly update their street value

seems all too unnecessary