A key distinguishing feature of effective altruism is that it aims to spend resources in a way that approximately maximises expected value.

Defending extravagant purchases for community building because the decisions have positive expected value, is committing a Motte and Bailey fallacy, with the Motte being “we should maximise EV” and the Bailey being “we should make positive EV decisions”.

Donating to your local opera house has positive EV too.