That meter simply boosts your chances, the best drops I've had I had with zero meter. I have no doubt it is accurate in terms of math, it's not just a graphic but seems like that half the time - but we are dealing with RNG. Exp is maxed out at 150 mil regardless of level, think that maxed out about level 178 or something, at levels below that it was less because it would give you a good chink, don't think it can ever give you more than 1 lvls XP. Level 172 I think it was around 110 mil. The whole concept with most things is that it can be done for free without paying GG but it will take forever, but if you want to really achieve anything with it get your wallet out. It's not a dig, it's just how it is. At the end of the day the guy running it doesn't do it for charity, he must have costs to cover and would want a little money out of the work he puts, why wouldn't he. It's optional.
I completely the understand the requirement for gamegold for the longevity of the server, I was just on about the keys drop rate and how the meter doesn’t seem effect anything just like you confirmed.
The meter is just useful for the demon souls quest in my view and has zilch effect on anything else, thought the same about heroes league when I was in that at level 155 lol.