> Similar surgeries in the States have cost my insurance north of twenty grand.
I'm assuming you're referring to the amount your insurance company had to pay, not the amount that you had to pay. If so, keep in mind that the prices insurance companies pay for procedures are not designed to make sense on an individual level[0].
I've explained this in more detail on previous comments, but basically, hospitals lose money on publicly-insured patients (Medicare/Medicaid), and so they have to make up the difference by overcharging private insurers. This is why the sticker price for procedures is so heavily inflated - they're intended to be the starting point for negotiation, and the insurers then negotiate standard rates (still inflated, but less so) for in-network providers.
In other words, the amount that your insurer had to pay for your ECG includes an amortization of the amount of excess cost that your insurer bears in order to (effectively) subsidize the patients on public insurance.
In theory, this should not affect your out-of-pocket costs (though of course, in the end, it all does come out of patients fixed monthly premiums, so you still are paying for it in some way).
Yes, this is unnecessarily complicated, but that's the way billing works.
[0] That is not to say that the amount that the insured patients pay for procedures shouldn't make sense on an individual level - just the amount that the insurer pays on top.