Steam collects GST so they've already figured that out.
But your basic thesis is correct, it's not apples-to-apples. Debit vs credit is a significant difference. Another major issue is that while the regulations for any one of the alternatives on my list aren't particularly onerous, I imagine the superset of all the regulations/contracts might well be.
I'm not sure how exactly Steam pays local taxes, be it a Canadian third party that siphons the extra money for them or if they just send each region the tax money, but either way the money is flowing abroad at some point. Then there's individual transactions. If you need to internationally send someone money and the payment processors say no for any reason, you're largely SOL. I guess you can mail cash directly, while that still exists. But my point that you can basically only go either through Visa/MC or through crypto stands, even though I don't particularly love either.
But your basic thesis is correct, it's not apples-to-apples. Debit vs credit is a significant difference. Another major issue is that while the regulations for any one of the alternatives on my list aren't particularly onerous, I imagine the superset of all the regulations/contracts might well be.