Ten Treasure Parcels Per Level
The way the experience tables are setup, if five characters encounter five monsters and everyone is of the same level, the characters (assuming that they win) will receive roughly one tenth of the experience points that they need to reach the next level. For every ten encounters then, the group will each gain a level. The Dungeon Master's Guide (starting on page 126) lists ten treasure parcels per level (1-30). Each encounter receives one treasure parcel. Therefore at each level, the group of adventurers has ten encounters and receives ten treasure parcels that they divvy up among themselves.
The ten parcels combined contain four magic items, coins and various other treasures. The magic items are 1, 2, 3, and 4 levels, respectively, above the level of the treasure parcels. Ten level one treasure parcels then contain: a level 2 magic item, a level 3 magic item, a level 4 magic item, a level 5 magic item, and coins and other treasures having a monetary value of 720 gold pieces.
How Much Is A Treasure Parcel
Aside from the magic items, the ten treasure parcels at each level have a total monetary value of 720 gold for first level, 1040 gold for second level, 1355 gold for third level, etc. If you chart out the increase from one level to the next, you get a very unusual result. At second level, the monetary treasure increases by 44% over what there was at first level. At third, fourth, fifth, and sixth, the value increases by 31%, 24%, 19%, and 80% respectively.
A Very Strange Progression
That's a very odd progression by itself. Weirder still is that the next five levels increase by the same exact amounts: 44%, 31%, 24%, 19%, and 80%. So do the five levels after that and the five levels after that all the way up to level 30. Someone intentionally wanted a level 25 treasure to be 19% more than a level 24 treasure and then have a level 26 treasure be 80% more than a level 25 treasure. For the life of me, I can't begin to fathom what they could have been thinking.
Let's Flatten That Curve Out A Bit
If you average those values out, you get a 40% increase every level. That makes a little more sense.
If you like the idea of treasure parcels, you can leave them just as they are or modify them so that each level gives 40% more monetary treasure than the previous level. I would have done so myself to include in this article but I don't like treasure parcels so that's not the direction I'm headed.
I prefer more randomness than that. Therefore, I'm going to work up some treasure tables that I will post to the downloads section when they are complete. I'll use a steady increase of 40% over each previous level as a guide. Switching from treasure parcels to a treasure table system will also allow me an opportunity to incorporate a couple of other changes that I want to make.
Denominations of Coins
Currently, 10 Copper = 1 Silver, 10 Silver = 1 Gold, 100 Gold = 1 Platinum, 100 Platinum = 1 Astral Diamond (Player's Handbook, page 212). A single level one encounter yields 72 gold. Copper and silver are basically worthless and Astral Diamonds (worth 10,000 gold) had to be invented to deal with the huge amounts of money being exchanged.
Instead, I want to shift the standard downward in order to bolster the copper and silver piece and lay the groundwork for a reworking of the economy that I plan to do soon. This will also do away with the necessity for the Astral Diamond. My system will have an exchange rate of 100:1 at each step so 100 Copper = 1 Silver, 100 Silver = 1 Gold, 100 Gold = 1 Platinum. Treasures will then be calculated in Silver Pieces instead of Gold Pieces.
Exactly the Same, But Different
This does NOT mean that characters will receive less treasure! Instead of ten first level encounters paying a total of 720 Gold, they will pay 720 Silver but everything characters need to buy will also cost silver instead of gold. What it does mean is that characters can find one tenth as many coins to equal the same relative value. Five gold now will have the value of five hundred gold under the original system but weight only one-tenth of a pound instead of ten pounds.
Imagine that you had a job somewhere that paid you 60,000,000 gumballs a year and that your expenses were 4,500,000 gumballs a months. You got tired of that and transferred to a new job that paid $60,000 a year and that your expenses were $4,500 a month. It works out to exactly the same thing. It's all just a matter of scale.
EDIT: See also How Much Treasure Should You Give Out (Part 2).