LCS Mid level 18 support level 12 ...

Let me guess the Mid laner also has about 400 more cs than the Support, and probably about 6 more kills right?

Also solo lane exp vs duo. That support also roamed an incredible amount from the looks of it, getting even less exp.

First of all, that's pretty much impossible to reconcile between all ELOs. Because how much gold a solo laner generates would be dependent on their skill to farm. While supports gold gen are for the most part, independent of such skill. (except for pocking shield or FQC) Often times in my Elo, I'm not even that far off from my lane counterparts. Especially on poke heavy supports.

Secondly, there's a limit to how much gold you can give to a Support, without it becoming a problem on other laners. (But hey, FQC is a wonderful option for a mid laner. Right?) And if a support can keep up with his lane counterpart in High ELO, you have probably passed that limit.

Thirdly, it's support. The class least dependent on gold. Particularly true for the high level ELO players, Who can easily make plays with just their gold item, boots, and a sight stone.

I don't think you're considering that in this meta LCS supports are often roaming the entire time.

Because most of the support's income is from assists... high elo/pro games are low kill games... whereas for us plebs people die left and right.