Yes, 97% is like doubling the other 2 gems inserted on the same equipment, the resistance gems still exist, and there are also gems of cooldown reduction, movement speed and attack speed, for yellow gems are damage increase for type of skills (black sorcery per example), blue gems have increase durability and increase amount of gold, not sure if there are more.

Increase gold...from what type of transactions?!?!?

Could be that when you pick gold off ground, which drop from enemies sometimes it gets multiplied by a certain amount like 1.5, or 2, etc...

Remember some mechanic like that in a game I played, but don't remember which game now.

Just an opinion though, Gab will know better of course. So Gab care to explain, would you kindly?

The gold droped by monsters is increased by %, i've seen unique gems that have 10-15% gold increase, so if a monster usually drops 100 gold and you have a 10% gem then it drops 110 gold, the more gems in the equip the more gold. No idea if it also affects the gold drop rate, i would need to get a lot of those gems and then do some runs.

Reminds me of Gold Find from Diablo xD