Are there any surveys of economists on the determinants of healthcare price increases in the US, particularly over several decades?
This was actually already indirectly answered by the IGM forum.
In this question the forum asks economists the following:

The US spends roughly 17% of GDP on healthcare, according to the OECD; most European countries spend less than 12% of GDP.
Higher quality-adjusted US healthcare prices contribute relatively more to the extra US spending than does the combination of higher quantity and quality of US care (interpreting quantity and quality to reflect both greater American healthcare needs due to underlying population health and the delivery of more or better healthcare services to Americans).

With the following answers:
From European economists:

From US economists:

This answer (albeit only indirectly) suggests most top policy economists think there is some factor other than technology or quantity demanded that is leading to the increased cost of American healthcare. If you skim the survey some of the alternative reasons presented include increased barriers to entry for American physicians, a dysfunctional insurance system, and market power in the American hospital system.