How much do health insures pay out for therapies to alleviate back
pain globally, per year? Please substantiate.

"Globally", there are so many different systems of health insurance,
that it would be difficult to estimate. In many European countries,
for example, one has a system of public (or partially public) health
insurance; some Third World countries have no health insurance system,
or have a very limited one. How can one compare the spending on back
pain in Togo and in Norway?