D&D armour and weapon rules as written bear very little relation to reality - for one thing, a shortsword does as much damage as a longsword when you're getting stabbed. And bronze is not significantly inferior to pre-modern steel, it's just a lot more expensive. I tend to translate D&D armours automatically to fit the setting, eg in my Arcadian 'Ghinorian Hills' campaign the 'plate' armour would be hoplite style armour. I would however leave out weapons that did not fit the setting, eg two-handed swords in ancient Greece, and the 5e longsword seems more like an historical longsword, what earlier D&D called a bastard sword.
Looking at the 5e tables, for a Hellenistic setting I would keep the 1500gp 'plate' as full bronze harness, the excessive cost actually makes more sense here than it would in a high-medieval setting. But I would cut down the weapon table a lot. I think it might be best just to leave out the anachronistic weapons and have PCs with spears and shortswords, but I'd be tempted to raise those king-of-the-battlefield weapons to d8 damage, more to pre-empt player complaints. I might change the names to 'battle spear' and 'sword', say - the standard spear's 60' throw range indicates it's a pretty light weapon compared to the kind of thing a Greek hero would have used. The two-handed 'pike' does 1d10, and would make a good sarissa.