(The "Treasure" rating for monsters goes up to +4 for Dragons)
The range is not small if it is a dice pool at +4. Maybe rolling for each of the creature's Hit Dice, at the treasure bonus, and referring to a table for each dice, the higher the number, the better the treasure.
For example, for a 10HD dragon, +4 treasure, roll ten dice, at +4, and refer to a treasure table you make up, that has , e.g.
| Roll | Treasure found |
|---|---|
| 1-4 | nothing |
| 5 | minor treasure, a few coppers, mundane, cheap items |
| 6 | minor, a few coppers and silver, mundane items |
| 7 | silver coins, quality mundane items |
| 8 | silver and gold, gems, art items, or minor magic item |
| 9 | gold, gems, art items, magic items |
| 10 | gold, gems, art items, major magic items |
something like that. So a dragon would get ten rolls at +4 on this table, making a substantial hoard. Maybe I'll develop the table when I have the time and post it here.