There are a few things about the Al-Qadim setting that are different to normal Pathfinder worlds. Some just reflect the environment and use normal PF rules, others are specific rules that come out of the original setting, updated for pathfinder.
Temperature
Zakhara is in a very hot part of the world and standard heat penalties apply. Because of this, next to no-one wears heavy, or even medium, armour but relies on lighter materials. Walking into town dressed in plate armour (or something similar) will attract the notice of the town guards, and others. Favoured armours in Zakhara are leather, studded leather or chain shirts.
Trade
Zakhara is a land of traders and merchants, there are few shops selling items at fixed (or book) prices you are expected to haggle over the price. Haggling is a new Charisma based skill.
Trained Merchants have an advantage, in that they know the ins and outs of the market place, the general conventions of trade and where to find the best wholesale prices. To qualify as a merchant, a PC must have an agreed Background, Trait or Feat that references Merchant, Trade or Business – or have spent 5 ranks in Profession: Merchant.
Buying in Bulk is the core advantage of the Traveling Merchant – They can buy a job-lot at rock-bottom prices, transport it somewhere else and sell it for a profit. The better the deals, the bigger the profits.
Merchants may buy any common item in 1,000-unit lots if the item’s price is listed in copper or silver pieces. If the price is listed in gold pieces, merchants can buy the item in 100-unit lots. After paying bargain prices, they sell the items to another merchant elsewhere (not in the same city) for the normal price. The merchants, of course, pocket the difference. Only items typically available in bulk can be bought and sold this way. For example, a merchant rogue would not normally be able to purchase a hundred ships over the counter. The DM has final say on whether a given product is available in large amounts. Magical items and objects listed as “rare” or “unique” are never available in bulk. To receive this benefit, a merchant must oversee the entire “bulk buy”—from purchase to delivery.