From some rough calculations, it looks like the show ran for about 550 performances. This comes out to about $273,000 per show.
Presumably, this was just the development costs associated with the hardware, music, animation, programming, etc. The ongoing operational costs (pyro, crowd control CMs, maintenance, replacement parts, etc.) would be additional expenses not factored into that price.
As a point of reference, DL’s Light Magic cost $20M to develop, and ran for about 100 nights (with 2 performances typical per night), giving it a development cost around $100,000 per show. Adjusted for inflation from 1997 to 2021 (when Harmonious debuted), that’s about $171,00 per show. Even in the (relatively small) pantheon of Disney parks’ costly high-profile flops, Harmonious is in a league of its own.
Given how reluctant Disney has been in recent years to spend big on new entertainment, it’s that much more surprising that it’s being abandoned entirely, rather than trying to salvage and rework parts of it.