I have implied no false dichotomy. I haven't said one must accept either or. I've said simply one can account for the costs implied by the OP without rejecting the sunk cost falacy.

If it helps you to think in sunk costs that's probably fine. I don't care. My point was purely that one can incorporate the kinds of concerns the OP was proposing without rejecting the "sunk cost falacy".

The dichotomy does seem to apply perfectly well. The cost of the ticket is sunken. The social cost of skipping the concert is not.

imagine every instant in your life is an infinitesimally small point on a timeline (or every millisecond if something concrete is easier). the present is t0.

an event occurs (buy ticket) at tX. according to "ignore sunk costs", at tX+delta you should annihilate all influence from any event at tX or before. therefore that you have a concert ticket is, in a weird way, almost immaterial. it enables a future decision (to "freely" go to a concert, as you would any other activity) but, my interpretation is that you only have present and future after every instant moment.

you may say: well what about eliminating future opportunities? e.g. i spent my last $250 on concert ticket so can't go to hawaii. that is in part of a matrix i would call "regret" or counterfactuals (not sure if there's an economic/scientific term here), which involves thinking about how past decisions affected future ones.