About the most unrealistic thing you can do is think in terms of the modern value of gold. Across history gold:silver value ratio was only about 20:1, falling to 10:1 in some gold producing areas. I rem from Classical History class that during the Peloponnesian War the ratio in Greece fell from 20:1 to 10:1 due to the influx of Persian gold - Persia backing the Spartans against Athens. And a silver piece was a pretty typical day's wage in many eras.
PHB arms and armour prices, along with some adventuring gear prices, definitely are inflated though - dividing by 10 (ie 'silver standard') would give prices much closer to historically accurate. The arms and armour are on 'adventuring economy' prices - and so are potions of healing, of course. This is deeply embedded in D&D norms and I don't see an easy way to change it; but you can make some cheaper gear (& potions) available in your game.
Edit: On the non-adventuring-economy scale a GP seems to be about $100. On the adventuring economy scale it's about $10. These aren't really reconcilable, the best we can do is fudge it a bit.