I think Tailish raises some very important points.
I've lately also come to realize that any pet that used to sit "below the gap" on the "Mainlist" is completely left in the dark right now and there are way too few trades on the Successful trade thread to support any decent value terms.
I'd personally agree that the focus sits on the wrong pets, but I don't really know how we'd strenghten the impact of lesser valuable pets without building a hierachy or finding a similar currency term (other than Mid-advents).
Whenever pets of the old "Advent, September" Lists are names, MA-values or 09-rares quantities are quoted from the old list. MAny of the pets mentioned sit on completely wrong tiers and are still traded for lower values, as the list is still the only guide accessible when trading such pets, that gives an easy-at a glance value.
The community desperately needs to emphasize actual knowledge of trading and we all need to help players to understand how values are created instead of giving them a blanc check with the current trading norm printed on it. That's not fair to either side and also way too rigid to reflect a real market.