The Pernese Economy has, since almost the very beginning, been based on barter, the concept of trading for something of equal value. Even after AIVAS, and the end of Falls, this concept is still practiced, and probably
will be practiced for some time to come. The question, though, is how does one know how much something is
worth? Or how much someone's services are worth? Or if one person doesn't have something that the other person will want? The answer is the staple of the Pernese monetary system: The Mark.
The Mark is not supported like most RL monetary systems on some sort of priceless metal; its sole foundation is daily labor. And while it fluctuates a good deal, from service to service, it can probably be roughly summed up that the Mark is the equivalent of work that the average man can do in an average month's work.
For example, a Harper's Apprentice makes a instrument. The Harper got the wood for the instrument from an Apprentice Woodcrafter. From beginning to end, the process would take the average person about a month.
Since the Apprentices in question are not much more skilled than the average man, the instrument would probably be worth a Mark. If a Master had done the work, the quality would have been much much finer, and taken probably much longer, and would not have been easily equalled by the average man, so would be worth much much more, depending on what the Master wants, and what he can get in trade for it.
So how much would one make, on Pern? Well, as another Science Fiction writer wrote, "There's no such thing as a free lunch." Not on Pern, at least. Take, for example, a cotholder. He works in the fields, very hard, doing over twice as much as his other fellows in as much time, and working numerous extra hours. Thus, in theory, he should be making
quite a bit of money. However, on the Northern Continent, there are only 15 legal landowners, total; the Lords and Ladies of the Major Holds. Everyone else - including Halls and Weyrs - is just 'renting land', though the Halls and Weyrs have gotten a different deal than normal people do. So the cotholder, mentioned above, is actually renting his
land from the local Holder, who is in fact renting it from the Lord Holder. Instead of rent outright, though, the Holders receive tithes from their holders; the actual 'pay' that the cotholder receives, generally, is whatever extra he produced that the Holder didn't take from him. Thus, unless someone deals a lot with traders, or provides special services, one does not usually have many Marks; perhaps an extra quarterMark (average week's work) every month.
Since it is based on Work, the Mark's standard value is determined every Turn by the Craft Council. Barring serious incidents, such as famines or plagues, or serious overproduction, the value of the Mark would stay pretty constant from Turn to Turn. The advent of the End of Fall, and the development of new technology, however, has cause a little destabilization and a lot of fluctuation in the value - especially as far as the more technologically influenced Crafts go.
With the freeing up of the Weyrs from fighting Fall, the Holds are no longer bound to tithe to them. Instead, the Weyrs would have to purchase their supplies from the Holds and Halls, and thus need to provide special services in order to earn their keep. As dragons can quite easily accomplish in a matter of moments what the average man would take some time to do, a the riders could quite easily command a tidy sum for their services, and still be cheaper than anyone else without a dragon; thus the second factor in destabilization. However, this has not been so bad, for two reasons. First, since the 'riders have to do it to support themselves, they would not be so quick to lessen what they can get for their services; second, non-Weyr 'riders now exist, and can undercut the Weyrs' costs, with their supplement from the land they work, keeping the Weyr-riders from charging too much
After the standard value has been determined by the Crafts, a limited number of Marks is distributed to them; with these, they get their supplies from the Holds, and services from the Weyrs. The Holds then use the Marks to purchase services from the Crafts, or from the Weyrs. The Weyrs use theirs to purchase Craft services, and Hold supplies.
Thus, a healthy circulation of money and a healthy economy is possible.
...And, for any economists who say that this is impossible, it is just a fictional series of books; relax. ;)