Aestas has nearly as many forms of coinage as it does kingdoms. Most coins are roughly similar in size and value, assuming 250 standard coins per pound, while pennies vary wildly in size and composition - all are small. These currencies have been closely aligned over the ages by a combination of historical factors, convenience, coincidence, and the use of magic to assure purity and consistency. Use the chart below for flavor for the major currencies in use in the Known World. There are countless other coins and currencies in use, but these major ones can generally be used anywhere successfully, with little loss of value. Larger denominations are of course possible, such as the $20,000 gold 1lb ingot, but these three are the most common sorts of coins. Most of the time, it is unnecessary to specify which specific coins are being used. This can simply be abstracted as "$" unless flavor is desired.
This article focuses on equipment of interest to adventurers, warriors, and other heroic types. Equipment prices and descriptions are primarily from GURPS Low Tech. The most common tech level for items found on Aestas is TL3, though many items from TL0 to TL2 are still in common manufacture and use throughout the known world. TL0 gear is often so rustic and primitive that it can be had for a fraction of the list cost, except in the case of armor. Fabric and leather remain in common use for light armor in most of the Known World, as both are ubiquitous and inexpensive. The most common metal armor is mail (or "chain mail" as it is sometimes called); despite being TL2, it remains relatively cheap and easy to mass-produce. "State of the Art" technology is described as TL4. All TL4 items are double the listed prices, and are somewhat limited in availability. They can usually only be found in major urban areas, trading or manufacturing centers, or in the hands of the wealthy and well-connected. This is especially true of things like plate armor and black-powder firearms. TL4 armor is not uncommon, but it is expensive; possession of a full suit of plate armor indicates that the wearer is a person of status and means. TL4 firearms are only manufactured in a few specific cities, and their place of origin can often be determined on sight by the knowledgeable. Most of these guns are matchlocks, though a few are wheel locks; flintlocks are not yet in existence. Normal black powder costs $50/lb, but it carries the "Salamander Curse". "Red Powder", the alchemical explosive developed to circumvent this dangerous issue, is $500/lb.
In addition to the mundane, real-world technology from GURPS Low Tech, a variety of equipment is available from other supplements. GURPS Dungeon Fantasy 1: Adventurers has a lengthy gear list. Any of the options for weapons, armor, and shields are acceptable. Anything other than "Balanced", "Fine", or "Very Fine" requires some sort of back story or at least a 5pt "Unusual Background" to explain how the character came by his Elven Bow. The listed enchantments and magic items are not normally available off-the-shelf. Most major cities will have at least one place that sells concoctions, potions, and poisons... though they are often more expensive than list-price. It is a seller's market, after all.
As an additional resource, it is strongly suggested that one should consult the excellent "Marketplace", by Mike Cubbin. This unofficial play aid is a comprehensive guide to prices for most of the things an adventurer might want. The supplement is intended for the author's personal RPG setting, but the shared assumptions are quite similar to those in Aestas. It can be safely consulted for anything other than armor and weapons, which are both discussed above. This rather large file is available in PDF form at the link below, and well as via Google.
"Marketplace", A GURPS Play Aid by Mike Cubbin (4.36MB, PDF)