[Espy]

IMO, the most expensive items are:
Tier 1: Full Anka Set
Tier 2: Year 1 Yearlies, Dragon Lord, Helias, Cyber Reaper, Rave Fever
Tier 3: Pandora's Boxes, Evo Items, majority of Japan items, Desert Nomad (surprising, huh...wasn't this an ADI?)

As for the other pre-Yearlies MDIs...
USB and Inventor's are probably around Tier 2, though those don't seem to get traded around much. Seabreeze, Feather Folk, and Woodland Archer are Tier 3 or lower, which is strange, considering their age.