There is a full-fledged Gaia Market. Market is divided into four parts - Shops, Trade, Marketplace, and Gaia Cash Shop.

Shops: There are various shops where NPCs sell different items for avatars, house, cars, etc. These shops are of all types, upmarket as well as economy. A player can buy items using gaia gold or Gaia Cash. Items found in the shops can also be sold back to the shop for 50% of the shop price.
Trade: Users can trade items and gold with other users.

Marketplace: Users can have up to 10 items for sale at once. The cost of this convenience is a 2% tax on all gold earned from sales, a feature implemented with the recent remake of the Marketplace.

Cash Shop: Also known as “La Victoire,” it is the most recent addition to Gaia’s economy and sells items for gaia gold (which itself is bought with real money). It includes high end items and special “evolving items” that change over time with the “evolving item reports“. You can also purchase “Monthly Collectibles” from the Cash Shop. Items are always subject to be rotated in and out of the Gaia Cash Shop.