In-game prices of items say so much about the game. Many Final Fantasies price Potions super cheap and Ethers not so much. Ethers were first sold in FF2 and cost 2500 gil. You could get fifty Potions for that much money. Made using them feel like a big deal. I still hold on to them much more cautiously in games, no matter what the relative price.
With the game starting with both Ethers and Potions for sale at 500 gil, FFEX is clearly telling the player to go ahead and use them.