How much gold do characters and monsters get through the level progression of 21-40?
Pathfinder doesn't include much detail for levels beyond 20
Pathfinder's rules don't cover advancement beyond level 20 in very much detail. You get guidance on what attack/save/spell progression for advancing classes should look like, but beyond that it leaves things very much up to you.
Mythic tiers, as linked in your comments, are a different system of progression which is separate from normal character level. A character with mythic tiers is treated as having a slightly higher level for the purpose of calculating encounter difficulty:
To adjust a character’s level, add half his tier (minimum 1) to his total character level. So a 10th-level/5th-tier character is effectively a 12th-level character for challenge and reward purposes, and a 20th-level/10th-tier character is effectively a 25th-level character for those purposes.
To adjust a foe’s CR, add half its tier or rank (minimum 1) to its CR. So a 2nd-rank minotaur is effectively a CR 6 monster, while a 6th-tier champion pit fiend would be CR 23. For mythic monsters, this calculation has already been made.
But in terms of their expected wealth, there is no difference between a character with mythic tiers and one without:
Note that mythic characters will face fewer encounters to reach their next character level, but their XP and treasure totals should still fall relatively close to those of a non-mythic character of the same level.
Pathfinder doesn't offer any rules or guidance on how much wealth a character above level 20 would be expected to have, though the table of expected treasure rewards per encounter does include entries for encounters up to CR30.
You could refer to 3.5e's epic progression
If you really are taking characters beyond 20th level, there were more detailed rules for this back in 3.5e's epic progression rules as given in the Dungeon Master's Guide, including a table for wealth-by-level up to level 40 on page 209. For levels 1-20, Pathfinder's expected wealth by level is roughly congruent with 3.5e's expected wealth by level - it seems like adding ~10-15% to the 3.5e values gets you to the Pathfinder figures, so you could do the same with 3.5e's values for levels 21-40 to get approximately sane values for Pathfinder.