Maybe you're a new player or just never knew this, but potency runes (the square ones) used in enchanting are available from the Enchanter vendor at 40-60% CHEAPER than guild stores. The reason I post this is that the lowest level runes have the largest percentage markup, which can only be supported by new players who don't know. The pricing on guild stores should be lower than the vendors, but it's not on many runes.
This applies to almost all runes until you get to close to CP 160 when the supply from the players is much higher. Check it out and hope you save a little in the process!