In my experience, with the warrior and archer at least, the 'best' item of each kind seems to stop at 96,000G in the shops. There seems to be a best armor, best helmet, best shield (warrior only)
for the warrior i already have...
Artemis' Chestpiece (armor):
Emerald Aegis (shield):
Warlord's Battlehelm of Doom (helmet):
and for my weapon...
Warlord's Fiery Blade (sword):
and there has to be at least 2 or 3 more missions. i'm about to do the mission where you save the towns lieutenants. i'll post again after i've beat the game but i hope i haven't already gotten the best weapons and armor. the shop hasn't been offering me anything new though... and i've had the sword, the helmet and the chest piece for at least a couple missions if not more.