I can't figure out how it works. My Sorceror has a shield with +76% more gold from monsters, but it doesn't seem to make any difference.
Does this affix maybe change the CHANCE of gold dropping from monsters, not the AMOUNT of gold in each pile? Just a random guess, I really have no idea.
You can try clearing the same level in full with and without the shield and compare those two piles of gold. Should be a big enough pool to test this, i personally never cared for gold too much so i can't tell if it's working or how.
Too small of a pool, like 20-30 monsters. I'd say clear cathedral lvl 4, on Torment preferably, normally it should be 60-80k gold, and with the shield you should go up to 1mil gold.