(I make a few generalisations here, beware)
Economy of scale is a factor in the production of maille, especially in Europe during the early medieval period. During much of the Roman period, iron was mined - mining (espeically deep mining) is an extremely labour intensive activity which can only be supported by a stable and sophisticated economy. The benefits, however, are the smelting of highly concentrated ore to create metals with few impurities. Thus, the prevalence of lorica segmentate (plate armour essentially) at the height of the Roman empire.
In the later Roman period civil war had broken out, and the gift-economies of the 'barbarians' took over as the predominant system in Europe. These economies do not rely on gold or silver as a means of exchange, instead using domestic livestock as the unit of account. In these economies, large scale operations for mining are extremely difficult. So, much of the iron used becomes that which is found close to the surface, or bog iron. This is full of impurities and required a lot of processing to get workable metals (for example, the technique of pattern welding is used to overcome the inherent weakness of steel made from bad iron). In this case, creating wire is a better substitute; it's relatively easy to produce at scale, and requires less processing as a steel plate would. The gauge is thin and the inner-diametre is small (6-9mm) so uses little material. 'Knitting' the wire together is quick and can be done with finger strength alone before the rivet is tapped, enabling low-skilled labour.
These factors make maille a relatively 'cheap' product compared to plated armours (scale, lamellar, full plate harnesses etc). Later, when silver economies reassert themselves (~600-900AD), the production of maille becomes a viable option on a larger scale, then as economies stabilise under the feudal lords of Europe (lots of tax income again), plate becomes possible again.
In terms of raw material cost, we can look at bloomaries excavated in Iceland for clues: they found approx 5000kg of iron slag, containing 45-600% residual iron oxide representing possibly 1400kg of raw iron blooms. This would require approx 6400kg of iron bog ore and 22000kg of charcoal. After primary and secondary smithing, this represents about 370kg of bar iron. At 8-10kg per raw bloom, this is about 140 smelts - with 3-5 metal workers, this is about 9000 man hours - that's before starting to work it from bar to wire/sheet!
In terms of monetary cost, the Scandinavian unit of account (~13th Century) was a good milking cow of not more than 7 winters (or 120 standardized iron ingots c. 12.3kg).
Assuming 12.3kg is enough to make the necessary wire and rivets for a 8kg shirt, this gives us a good idea of a modern cost - it's about £1500 to buy a cow in the UK at the moment. Add in labour and I reckon it would be the price of a small family car. (In period, giving up food and a source of income - milk and meat - would inflate the cost by quite a bit!)
Smith, K.P., Ore, Fire, Hammer, Sickle: Iron Production in Viking Age and Early Medieval Iceland
Skre, D. (Chapter 3) Silver Economies, Monetisation and Society in Scandinavia, AD 800-1000