Wealth is measured in Tiers from 0 to V.

TierLimitDescriptionTrade
05spbasic services (food and lodging), simple adventuring gearnone
I5gpsimple weapons, light armours, leather helms, wood shieldslocal
II10gpsimple weapons, light to medium armours, wood helms and shieldsshort distance
III100gpexotic materials and weapons, medium to heavy armours, steel helms and shieldsmedium distance
IV500gpall weapons, armours, gear, mounts, special items and siege weaponslong distance
V1000gpmagic items and serviceslong distance

The Limit determines the maximum value of a single item, that can be bought, sold or found. Anything can have a Wealth Tier, and has to be interpreted in this context. Examples include:

The values given are an example that fits for most Old-School RPG systems, but you might need to adapt the exact values to your system.

Haggling

The Limit is always to be applied before haggling. Even if you would manage to haggle down a 12gp item to below 10gp, a Tier II settlement for example would still not carry that item in the first place. Similarly when selling items. If a gem is worth 20gp, you could not sell it to a Tier II settlement, even when the shop-owner is haggling you down to 10gp. You always take the base price to determine if it fits into the limit or not.

Community Wealth

Community Wealth is always 10 times the Limit of that Tier. That means you can maximally buy or sell 10 items of the same type. You can roll 1d10 (or 1d6+4), so determine the actual number of items available for more variance.

Specialists

Even though you might be limited on what items are available in a Tier, you can still allow for certain items to be acquired, even if it does not belong in that Tier. This can be achieved by so called specialists.

For example an old witch, that brews curious potions in their hut next to a village. The villagers go to the witch to cure their ailments and more. So even though the village might have Tier 0 or Tier I, you could still get some potions from that witch - which normally cost more than the Limit.

However she might not want coin or gems for their services, but require other favours or trades in exchange. Or they just require the ingredients which are hard to get.

Rewards

When trying to determine the Tier of a reward, consider the rank of a dungeon, Progress Track or Tier of a faction. You can also shift that Tier up or down by rolling a d12.

d12Reward
1-2Tier - 1 (min 0)
3-7Tier
8-11Tier + 1 (max 5)
12Tier + 2 (max 5)