The drops that you collect from killing foes in PvE gameplay should be sufficient to cover your typical PvE expenses. However, when you go for the high-end "perfect" and "green" weapons and "prestige" armor, that is when you will see prices skyrocket. Be aware that many of these weapons, armor and items were put into the game specifically as a "gold sink" for the wealthy players. In most cases there are alternative items that have equivalent stats, but are much cheaper. Go for the cheap alternative. For example, a perfect sword pommel of Fortitude (+30 health) can cost thousands of gold, while a pommel that only provides +28 health will only cost a small fraction of that. Be sure that you have done your homework and know your options before spending huge sums of gold on an item.