Monthly Collectibles '"Donation Items"' are special items that can be bought with real money meant to support Gaia's maintenance and costs. Established in June 2003 after users of Gaia Online petitioned for a "donation system" in an attempt to increase site revenue, for every US $2.50 a user gives to the site, he or she receives an item known as a "Sealed Envelope" in his or her inventory.
On the 15th of every month, the Sealed Envelope disappears from the user's inventory and is replaced by a "Thank You Letter" for the current paid month (for example, a "Thank You Letter for August 2004" represents a payment made in that month of that year). Users are then able to "open" these virtual letters to choose one of two or three limited-edition items to be granted into their inventory from each letter. These items were known as Donation Items until potential legal problems prompted the name change. Monthly Collectible items and the "Thank You" Letter items they are found in are specific to the month that they were released in: for example, the items found in the "Thank You" Letter for April 2006 can only be found in that letter, and one could only purchase that letter in April 2006. Letters can be purchased over the phone, with a text message from a mobile phone, via PayPal, credit card, traditional mail or with the aforementioned Gaia Cash cards.
Users can also purchase these Letters and specific Letter items from other users for gold via the Marketplace (see below). Because of this, many Gaians sell Thank You Letters each month to earn vast amounts of Gaia gold.
Gaia now also offers 'Gaia cash', which is virtual money that may be bought using actual money. For example, one dollar is equivalent to 100 Gaia cash. Gaia offers Gaia Cash Cards, in ten, twenty-five, or fifty dollar amounts. It includes a pin number that a user can enter at the redeem section of Gaia.