Many visitors at living history events are interested in the value of the equipment shown. They don’t want to know the prices of the replicas at re-enactors markets, but what a Viking or a Frisian or a Saxon would have paid for the real thing, a thousand years ago. Visitors seem to be especially interested in the prices of swords. The price of weapons is also interesting from an authenticity point of view. At show battles or weapon demonstrations, most re-enactors wear swords, but does this reflect the early medieval reality? Were swords not reserved to the richest warriors?
If you search the Internet or your local library, you might come across some interesting answers to this question. One web article says that once there was a sword exchanged for 25 head of cattle, and another was swapped for a whole village in Wales.  A German website figures out that in the 8th century a full warrior's outfit would cost the equivalent of 30 cows.  Finally, a recent Dutch exhibition catalogue presents a list of Viking-age weapons and other items, with very precise prices in grams of silver. 
Since all this information is presented without the sources, it is uncertain how reliable it is, and whether it can be used as a reference for re-enactors. To fill this gap, I have done some research. I have surveyed texts from Western Europe in the early Middle Ages (about AD 500 - 1000): law books, charters, wills, sagas and chronicles.
Many texts tell us what was paid for land and for all sorts of domestic animals, or what fines had to be paid for crimes. Unfortunately, information on the value of weapons and armour is rare in these early texts. Only twelve sources (the ones mentioned on the Primary Sources page) provided useable data.  The survey is pretty complete, as far as I know. If I still missed anything, please do not hesitate to tell me so at firstname.lastname@example.org.
The table below presents an overview of the twelve primary sources providing information about the value of weapons and armour, or other relevant data. The list is ordered chronologically. Look at the Primary sources page for a full description of each source.
The sources mention all kinds of currency. In order to make a comparison, I have converted each value into silver pennies. A money reformation took place during Charlemagne's reign, by the end of the 8th century. The old unit of account, the golden solidus, was replaced by the new silver solidus. The old golden solidus equalled 36 silver pennies, and the new solidus equalled 12 silver pennies. 
Prices of weapons and armour
The two table below presents the original prices as they were mentioned in the sources, and the converted values, for weapons and armour. Look at the Primary sources page for additional information regarding the prices and the conversion.
Prices of horses and cattle
For comparison, prices horses and cattle in the early Middle Ages are given below.
The table with weapons and armour shows a highly variable pattern, to put it mildly. It is hard to compare the various sources, because overall price levels differed through time and between places. Furthermore, there are some uncertainties concerning the types of weapons (basic or decorated?), and about the calculation methods applied.
The cheapest sword mentioned, from Brittany, was 'only' 60 silver pennies. This is still the equivalent of one to three cows. So a sword was not a weapon that every simple peasant could afford.
The scabbard and the fittings could increase the value of a sword considerably, as can be seen in Lex Ribuaria. Some swords had an astronomical value, equalling more than 200 cows. These were obviously unusual objects. From the context in which they are mentioned, it is clear that these swords were all owned by emperors, kings, or other noble persons. Charlemagne wore his fancy jewelled sword only on special occasions. Such swords made the medieval headlines, but they should not be taken as a reference for the ordinary swords worn by common re-enactors on an average Bank-holiday.
Similarly, the shield and lance in Baldric’s donation may have been unusual. These items were part of a gift to Saint Maarten's church in Utrecht, and apparently special enough to be documented. Therefore, I suppose that the shield was not just some plank of wood, but that it must have had artistic decorations or precious materials applied to it. An ordinary lance and sword, for use in battle, may have been less than 60 pennies.
The sword fittings from Norway look cheap, but the general price level here seems to be relatively low, if we look at the price of a cow. The worth of these fittings equalled 16 cows, which is quite impressive. Again, this was a royal gift. Interestingly, the Laxdæla saga specifies the value of the fittings, but not of the sword itself.
Early medieval weapons, and more specifically swords, were expensive and probably not affordable for everybody. However, if you could buy a few cows or a horse, than a sword would also be within your reach. Some swords mentioned in the written sources were extremely expensive, but this should not imply that only emperors and kings could own a sword.
I am grateful to the members of the Yahoo discussion groups Germanic-L and Authenti-Vike who helped me with the translations.
 Nash, www.geocities.com/welshforge/welshwar.htm. The article does not give any sources. The swapping of a sword against the Welsh village of Roath may be based on a tale from the later Middle Ages.
 Willemsen (2004). A popular book with many great pictures, but no references what so ever. See also Kraus (2005).
 I have studied several other written sources from the early Middle Ages, but that did not yield any information relevant to our topic: Lex Frisionum, the Frisian book of law (Nieuwenhuijsen, 2003/2005); Lex Salica (MGH LL nat. Germ. 4.2); Leges Allamannorum (MGH LL nat. Germ. 5.1); the Dutch charter books (see overview at www.keesn.nl/names/en8_refs.htm).
As far as I know, the three wills mentioned, and the Laws of Ine, are the only early Anglo-Saxon documents giving values of weapons. According to William Short , the Laxdæla Saga is the only saga mentioning the price of a sword.
 The first version of this website gave AD 630 - 750 as dating for Lex Ribuaria. The law was indeed codified in these years, but the pricelist with armour, horses and cattle was added later. See the page with details on the primairy sources.
 Conversion table based on Henstra (1999) and Carlson (2005).